Many of us here have got to the point where we feel our marriages are in jeopardy due to step kids, bio mothers, or our partners' way of dealing (or rather not dealing) with them.   I just used to assume that everything SD24 said was a lie, until proved otherwise!  My DH would never know, or admit, that she lied a lot, whereas it was obvious to me. Hopefully you will feel less alone from being on the site - even if sometimes there is no solution to an issue like this, other than splitting up. 

I've been on and off the site for a few years.  Lots of support here.  One thing I know - when I split with ex, all I wanted was peace.  He brought so much chaos to my life.  Ex and are actually close friends now.  Anyway, many years later when I  met my current husband, I made it crystal clear that I wouldn't let anyone disturb my peace like that ever again.  The stepdaughters have cause us angst though - especially the older one but since they never lived with us, i was able to disengage pretty easily when I needed to.  Except for the 6 months older SD lived with us with her toddler and she was pregnant with #2.   I nearly lost my mind.  She asked why they couldn't just live with us when she had the baby.  I said to her: Look at me.  There's no way you can live here permanently.  we found her an apartment soon after.  He'll deny it but i know DH wanted them to stay.  My marriage would've fallen apart if we let her stay so I tyold him that I was miserable and as long as I'm miserable, he's gonna be miserable.   LMAO.  SD still drives me crazy.

I'm sorry for what you're going thru - no one should have to live with that chaos.  I would have them both leave and see if I could maintain a relationship living apart -  but that's just me.  Life is too short.  We're here for you though

I guess the first thing you can look at is your relationship with your SO.  Is it strong? Is it worth the struggle? Is he a good man to you?

Now, I would say as far as the last point, he has not beena great partner when dealing with his son's issues.  I mean, you are generously having him with you full time now (I'm guessing you had little choice).  And he can't do the bare miniumum to make the situation more bearable for you?

And please don't let me understand that he is angry at YOU when his son does poorly in school.

But if the relationship is worth trying to improve things.  I think you need to figure out what your hills to die on are.  What of his issues most negatively impacts you and your home life.  Start there.

It is helpful to try to phrase advice to your DH as being helpful for his son.  they need to learn manners because it will make them more successful. I'm afraid his life will be harder than necessary if he doesn't go to college etc...

Some of the issues you can simply disengage from.  Picky eater? doesn't matter if you don't have to cook for him.  If he doesn't like what is on the table? his dad tells him to go fix himself a sandwich... or bowl of ramen. 

A slob?  if it is contained to his room fine.. if it spills out.. you ask your SO to clean it up... he may see the wisdom of getting his son to learn to be more tidy if he pays the piper there.

And school... you aren't in charge of that.  If dad wants him to succeed.. he can help him and follow up... it's not your problem.

BUT.. your partner should clearly udnerstand that you won't be having a lay about 18 year old on your couch.. he is on his own at 18.

Read up on that on this site. It may become your BFF, your peacemaker, your bible.

Learn to ignore, direct SS to your DH, and pick your battles. Some are hills to die on,  others are bite your tongue worthy. Only you can decide what those are.

Communicate, communicate, and communicate with your partner as what you expect for a blissful home. Build your boundaries and stick to them. Do net let DH change them when it suits him. If you want to call lil Johnny names come on here and vent. WELCOME

Blessings in step life.

Look up The Burning Platform.