How do you not blame yourself? Stop doing that.

KISS.

Quit thinking with your fee fees and start using your brain.  Feelings and emotion are not analysis or decisioning tools.

I truly am not trying to be overbearing, though I know I can be.  

First, rekey the locks, have his crap packed up and taken to his apartment complex and let him deal with it.  Yes, block him and vector all contact through your attorney.  Do not forget to bill him for the half of the housepayment that he is responsible and you have been paying, bill him for management fees on the home, bill him for half of the repair costs, taxes, etc.....

His choice to wallow in his shallow and polluted shit puddle of a gene pool while embracing his XW's manipulative minions makes him and them a write off.

Life is too  precious to waste it on crap. They are all crap. Your, are not.

Categorize people by their actions and stop being fooled by their words and by your own fantasy of  being in love with the IDEA of him and us.

You know that there is no "us" and there really never has been.

I have a truth that has proven accurate for me.  I call it Rags' 3 Ray Rule. A breakup only hurts the worst for 3 days. Then beginning on day 4 it hurts just a little bit less each day until eventually it is little more than occassional though rare twinge of unpleasant memory.  Part of this truth is that if you re-engage, it all resets and you have to start over from zero.

You re-engage and reset your pain every day and IMHO, make zero progress. Even with the excessive effort you put in with weekly therapy, you have not ended it. You facilitate your own pain by not progressing through the process.  Had you remained on the grief and recovery path with a focus on the future you would be a significant way down that path instead of starting each day at the beginning and making no progress.

Never forget that it is about living your best life.  Also never forget that living well is the best revenge.

Start living your best life instead of diving daily into the cesspool of this dumbass's shallow and polluted cesspool of a life and gene pool.  You do not have to wallow in that crap.

So... don't do that.

He is not stuck. He is exactly where he wants to be as proven by his repeat choice to stay there.  Sadly, you too are exactly where you want to be as proven by your repeat choice to remain in this votex of shit.  It is you who  feels "stuck" because  you are stuck.   Yet it is you who is keeping yourself stuck.  Make a different choice.

No judgement. Just concern that if you do not stop this, you are doomed far worse than that dipshitiot XF is.

Stop circling the drain and take actual definitive action.

Take care of you. No one else in this shit show will.  If you won't do it for yourself, do it for your DD.  Your failure to move on is damaging not just you, it is damaging your daugther.

Stop that.

Your ex is stuck and he has got you to be stuck, too.   He gives you mixed messages all the time, so that you don't know where you are - eg leaving you and the house in a financial mess but now saying he wants to get married - really?  You can see how ridiculous it is.  I think you identified the trouble, yourself - ie you recall the "old" him who was a much better partner.  But he is never going to be that person again.  Stop believing it is your fault - your therapist should be able to help with that.  Your Ex is an adult, however inept - it is easier to blame you than look to his own accountability -  and he is probably going to be SD's carer all his life.   It is quite reasonable that you did not want to live with his daughters - I have also refused to do this in the past.  If DH wants to live with one of them I will not be part of it.  I have had a difficult life and I have earned some peace. I suggest that your only priority should be YOUR peace and your daughter's.  Get yourself a new therapist if the one you're seeing isn't good enough.  Take charge of your life and stop being pushed around by this man.  

I am so glad you can see right through him. Did you consult a lawyer? You said he's being difficult about the house - can you give us a bit more about that?

I would go no contact with him and force all communication through your lawyer. I  would also start stuffing anything and everything into garbage bags, one bag a day and stick them in the garage until there's nothing left. When it's done, let him know he has 10 days to come and get his gear or you'll dispose of it. Make sure he gives you a date and sticks to it. Do not be there when he turns up  - have a friend or two to be there to supervise instead.

Having read over some of your past posts, it sounds as if he has much of the same mental issues as his daughters and alcohol plus mental health issues are an explosive mixture. 

As for him wanting to marry you... given his past behaviour... you'd need to be crazy. He probably thought that if you married him, he'd be able to force his daughters into your home so that he could have his daughters around all while benefitting from the home comforts that he misses. 

You're stuck in a rut you're keeping yourself in. I think you need to ask yourself why you're willing to settle for being in it. Do you think you're not worthy of better? Do you think you're deserving of his mentally unbalanced punishments? Do you justt not know how to climb out? 

All questions to deal with w/ professional help. Pop the happily ever after balloon you're floating ans ask yourself who you will be in 5 years, in 10. I wonder if it's not fear holding you down. Fear of starting anew and alone might be causing you to allow this situation to become your normal. I was raised in our home with a mentally ill and untreated parent and it affected me. I tend to hold onto the bad because I somehow became a people tender and I didn't want to be that person who gave up on someone I love/loved. It is a nasty rut to stay in. You sacrifice your own happy to coddle and help someone who is poison in your life. He is the only one who can change his situation, save yourself. Save your future. 

You are dealing with bipolar.  There is very little logic from them when they are spiraling.  Mania can be either ecstatic or mean.  Depression makes them needy or private.  None of it you can change.  They need to take charge of their own health.  They don't want to from the sounds of it so the best thing you can do is walk away.  Take your heart and find a better life.  Julie Fast has written a book for partners dealing with bipolar.  She says you have to put yourself first.  You can not waste your life trying to wait out unmedicated bipolar.   Let go now.  Don't spend another moment on this. You deserve better and the only one who can make that happen is you.  

Bipolar people are unpredictable, that's part of the bipolar.  Guest he felt bad for his DD. him giving her the bipolar she has.  his DD needs someone to take care of her.  If she can't keep a job of any type she must be really bad.  Hope she is on meds.  
'This is not the type of life you want to live.  Not be able to trust your SO.  
Let the lawer handle it.  Anything of his after 1,5 years is yours. It's abandonment.   Either you send it to him after he send you money for that, or sell it, throw it away.  
'Next time look closer to your next relationship.  It's hard to see mental illness,  s9 you really have to be on guard. 
I am sure he would love to live with you.  Not his sick DD.  That's why he is trying to keep the connection.  His bipolar stop him from realizing no one will Waite for him .  Since his DD was not pit in a home. He not going anyplace 

My ex was a classic NARC, something nobody really knew or understood back in the late 90’s all I know is he was like a drug to me, despite how horribly he treated me.  When I left him, it was like getting off drugs, I moved away and I craved him for weeks, months, years.  Because he made me feel a certain way that nobody else has been able to make me feel.  Now being older and wiser I understand that those feelings aren’t real or sustainable, but when I was with him, I couldn’t think past him.  You need to cut this guy off cold turkey and detox, get a lawyer to deal with and communicate with him from here on out.

It sounds like you may be obsessively ripping and picking at the wound. Its never going to heal. Try harder to go no contact.

And hey- no judgement here - there is no time limit on grieving the relationship that you wished and hoped for. Allow yourself time and space to grieve so you can re-start your healing journey. Talking about it helps. Writing it out here also helps. It always helps me to work it out by writing here and getting feedback or digital ((hugs)).

So -sending you a digital ((hug))

Even when someone supposedly and even legitimately has the syndrome or disorder of the moment, tolerating their crap is not mandatory. 

Unconditional love does not mean unconditional acceptance of crap behavior. Even for a special needs kidult

I know it is not exactly the same thing, however, as a T-1 diabetic I have had periods in my adult life where I have been a raging asshole. Mean as hell, and volatile. Never violent or physically aggressive.  Just massive irrational mood swings.

It could have cost me my then young marriage. If I had been my DW, I would not have tolerated me. Even a couple of dozen years later, the very thought of that chokes me up.

During a quarterly Endo appointment the doc and me were engaging on my diabetes, blood glucose stability (it was all over the place), and side effects of poor BG control. My rockstar Endo referenced a then recent study that tied volatile BG swings to massive mood swings.  At that second tears started pouring down my face.  I knew exactly what was going on.  I also knew that with that one small piece of new information that I owned the problem, and I owned both solution steps.  First, stop the asshole behavior. If a mood swing made no sense, do not go down the rageing asshole rat hole.  More affirmatively, diligently manage and control my BG.

Just the thought of how close I came to destroying such an amazing beautiful brilliant woman and a sweet tow headed little boy shakes me to my core.  Because I had failed to stop the stupid asshole rage inducing mood swings.  I could have not done that, even before we figured out what was causing it Eve with the physiological cause, that was entirely on me.  And, it was entirely on me that I lost the plot in managing my disease.

My mom was part of changing my course at that time, she basically kicked me in the ass, told me to knock it off before I ruined the best thing ever in my life, and said if I screwed up this marriage, she would end me. Not an idle threat from a 5'2" Southern bell mama who is a very out follower of the Elena Bobbit school of using kitchen shears to end an asshole man (not literally of course). Thank God.

I share this to highlight the point that why someone does these shit behaviors really does not matter. That they perpetrate these behaviors is what matters.  In my case, I learned why and had full influence out of fixing it. If I had whatever syndrome/disorder that caused it, I could still choose to not behave that way.  Anyone can and everyone should be held to that standard.

IMHO of course.

Support and direct the syndromed/disordered kidult to get help, do not tolerate the shit behavior.

That... is my life lesson and perspective on this general syndrome/disorder topic.

You can experience mood swings when your blood glucose levels are too high or low. Stress, depression, and anxiety can also crop up. Managing diabetes on a daily basis can feel overwhelming, so it's important to check in on your emotional well-being every once in a while.

Can diabetes affect your mood? | Diabetes Australia

I may be the outsider opinion here but why not just live separately while staying together. 
 

Blending families is HARD AF and if it will preserve y'all's peace to leave in separate homes (at least until most the kids are grown) then why not? Unless your are adamant about living in a traditional type relationship where everyone is in one home. 

You seem like a nice lady but his baggage is not nice.....Do you really want hassle of living with his mentally unstable unemployed daughters indefinitely just for the sake of having a warm body every night??? 

You are not going to be able to get over him until you quit interacting with him. I know it is hard when the feelings are still there, but this guy is not the one for you. You need to cease all contact and have everything about the house go through your lawyer. Yes, it will be more expensive, but it will be worth it. As far as the house, move forward on whatever plan you have and get it done. That is the last thing really connecting you, and once it is taken care of, it will be much easier to move forward.