It seems to me that you have invested a lot of time (18yrs I gather)  in your marriage and your lifestyle, and are reluctant to give that up.  However you said in your previous blog that your only joy in life was your cats. It seems that your DH has allowed his daughter to usurp your place in his life as first lady - and that if push comes to shove, he would choose her.  You are dead right he is enabling her. It's totally ridiculous that she is living with you at age 32, whatever her issues are. 

If you are avoiding going home and there is no joy there for you, or with your husband, in your place I definitely would be considering leaving. 

I would treat her like the child she's acting like.  If she's supposed to mop the floors on Monday then I want her to text me when when she's finished, maybe even require a photo of her work. I would also require a hell of a lot more than mopping the floor. She should be your chore bitch. You shouldn't be lifting a finger.  

"I guess nothing i do  is good enough for you." "I guess i just can't do anything right." "I guess i just can't make you happy, can I?"

If every step forward comes with a step or two back, everything has a "catch", and every favor comes with a punishment, yeah, those things are true and don't let him use them to manipulate you. 

You have all your answers written out for you here. He will choose her, he's only happy when he's around her, he gaslights you for her. I guess my question is do you want to grow old happy and healthy or do you want to grow old miserable and mistreated?

Since DH fails miserably at being a husband, time to rethink WHY you are there. He also is a shitty father.

Does not sound like you are doing well with this. News flash no one would.

Put yourself first and leave the toxic duo in your dust.

If you think you're unhappy now, just keep doing nothing. Things are going to get much, much worse.

You have a lot of power here, but you're afraid to use it. Afraid to rock the boat. Afraid to lose the business. Afraid to be alone. Afraid to lose your H. Fear is ruling your life and making you a doormat. Why do you think that is?

I've been with my DH for almost thirty years. Never once in that time has he even considered leaving me at home for three weeks to vacation with another woman. Your H left you home. In Alaska. In winter. Recovering from an injury. While he went to Florida. With his mini wife. For THREE WEEKS. Read this paragraph a few times. Why do you accept such outrageous neglect? Have you booked your own three week vacation to someplace warm?

It seems this marriage has worn you down to the point where you've lost your self and your self worth. Do you get that most women would not put up with this? You need to find YOU again, and gain some perspective so you can see just how crazy this all is. Treat yourself to some sessions with a therapist and talk to some divorce attorneys. Just let your relationship drift for a while and work on yourself. Stop letting fear run your life.

You know he is a classic enabler and you know there isn't anything you can do about DH or SD.

I know this isn't how you envisioned your life at this point. But THIS is your life, and it's not a happy one. What can you do to change it? You have to come to grips with the way things are, rather than the way things should be or the way you want them to be.

There is no need to rush to any decision. It took me 10 years to leave my exH, when I knew on my wedding day that I'd made a terrible mistake. So what do you need to do to gain some strength to make changes? One thing I highly recommend inindividual counseling, not couples counseling. You work on YOU, to define what you want and need. Find the happy person you used to be.

Right now all your energy is being sucked up by two people who care more about themselves and each other than they do you. Surely that's not what you want from a partner. Surely that's no way to grow old together. You might need to make some difficult decisions and do some things that you hate doing. But you CAN do hard things. You can find your happiness again, I know you can.

You worked on a rehab unit, so you know all about codependency. She's an alcoholic (maybe), he's addicted to her, and you are addicted to him. You are focused on changing him so he will change her, or just focused on her, so everyone and everything in the house is circing around the addict - which is how codependency works.

You can't change her or him - but you can disengage from focusing on him and her and take care of yourself. I wonder if something like Al-Anon would help you.  You are living with an addict and getting caught up in the cycle of codependency, and they are good at sorting that out - even if you do an online group or through Reddit or something of the sort.

Y'know, from where I'm sitting, it seems that you're the only one making an effort here. The business that you are scared of losing is all on your shoulders. Your job is incredibly stressful right now (and that isn't going to change in the near future. Having a mini-wife hanging around is stressful too. So, how about losing at least one item of stress. Tell your DuH that you are selling out your part of the business (get it evaluated by a professional first so you don't get screwed). If he wants to buy you out you want HARD CASH for it. No loans, no paying you back as and when he can. If he won't buy it, then sell your share on the open market (if that can be done where you live). You NEED to lose some stress and this is the part you can shed the most easily. Do it. If he doesn't like that, well, at this point, who cares? You'll at least have money in the bank to use as you see fit.

Frankly, I'd simplify the situation and divorce him as well and give him the option of buying your share of the house too. Just think, you could have your own place with all the peace and quiet you need where you wouldn't have to watch your DuH frittering away his (your?) savings on his sponging daughter. 

You HAVE to change something or your stress levels could kill you.

Doesn't sound like your SO has your back. You like being away from home...thats a sign. You are happier away from them. Why not make that permanent?