I learned over the years to never to argue about the step children. WHY? You will never win or feel good about it. All of my old conversations were about his Daddy guilt. These men don't see it. Mine never will. I consider it his psychological problem..

The SKs aren't the wedge. Your DH and his inability to see reality and react to that is the wedge. He wants what he had/has with his SM, but he's not taking into account how his dad supported that relationship and how HE supported that relationship. He's not taking into account that apparently his kids haven't gotten over the divorce. He isn't taking into account how they have/are failing to launch. He isn't taking int account that his kids may not want or care about a relationship with you the way he did with his SM.

Likely, he's uncomfortable and embarrassed that he divorced and couldn't make The Brady Bunch a reality. Instead of accepting that different doesn't mean worse, which would require him to look internally, he'd rather look for someone or something eternal to account for his perceived failures. My guess is he also blames the school, employers, former friends, BM, and anyone else he can for his poor feelings and failures. If he does admit that he failed, my guess is that he just makes a general statement and doesn't look any further as to what he actually did wrong.

My advice is to address the issue this way:

"DH, if I have been such a horrible person to your children, why have you kept me around? You can't have it both ways. Either I am awful, and you're a crap parent for keeping me in the lives of your children, or I'm not as bad as you claim I am, which makes you a crap partner for making me feel like sh*t for something you know I haven't done. Your kids and I have a relationship that works for us. What we don't have is a relationship that works for YOU, and it's awfully selfish to expect us to act differently in order to make YOU feel better. Perhaps spending more time with your kids would be good because your oldest is still having problems processing the divorce that happened when she was a minor, and you need to blame yourself for not helping her through that sooner. Stop blaming me for your failures, and either decide that I am worth keeping as a wife and treat me accordingly, or double-down on me being a b*tch so I can pack my things and go. Your choice."

"DH I'm not your punching bag for the trauma of your divorce, the trauma of YOUR SM and for your inability to help raise decent human beings. You poke at me ever again about your kids and you can spend money you don't have on another divorce." If my DH blamed me for his failings I don't think I could respect him enough to stay married.

Seems to me that your DH is the one who needs counseling. 

Guilty dads expecting the SM to treat these snotty skids with white gloves. It doesnt matter that they treat us like a dirty old rag we should idolize them and their (lack of) accomplishments.

Whats next you cannot ask them how their day was because that will trigger something.

If your DH cannot respect you and your time, F him. Its up to a parent to teach their kids about respect. Respect in letting you know in advance about plans. Sounds like your DH is treating you like a scapegoat. It is way easier to blame you, better you are upset than the snotty skids.

Let him argue, do not argue back. State calmly how this is unfair to you. If you do not respect our life together then please go and spend the rest of your days up their ass.

I can't imagine kids 18 and 21 wanting more daddy time.  Daddy money, yes, daddy time, no.  Most kids want LESS daddy time so they can do their own thing, you know like go out with their buds, smoke dope, shack up, etc.  Lol.

Happy, your problem was, is, and will always be your H. No, he's not normal. He's a selfish, domineering Ahole. He picked you because you're sweet and conflict avoidant, making it easier for him to get his own (screwed up) way. He likes having a woman (and her money) around, but on his terms. 

He and BM screwed up their kids. But of course, he'll never admit it and use you as a whipping boy instead. 

Guys like this only respect strength. I hate how he mistreats you, doesn't care about your bios, and caters to his bios while neglecting you. He is NOT a good man or a good H, and I wish you'd boot him from your life. You deserve better.

Oh please!!! I remember when we first moved in how if I even said hi to SD, it was like DH was ready to jump on me. I remember when I asked her innocently when she would come in the door "how was school? do you have a lot of homework?"  DH literally told me afterwards in an annoyed tone that I'm not supposed to say something like that because it implies I'm telling her to go up to her room and do it!! Needless to say we had a lot of arguments the first few years  that brought me to tears but eventually he has come around a little bit.
 

I can now ask her how was school and if she has homework or ask her about her new interest in playing soccer etc. without him freaking out. but it still feels like every time we're having a conversation if he's in the room with us it's like he's listening and watching and ready to jump on me. Even last night it happened. She went to put some pretzels in a bag for her school lunch today. She dumped half the pretzel bag into a baggie (which by the way, the bag of pretzels was brand new on Sunday so basically in two days she polished off an entire bag of pretzels herself but that's another topic.)  I just wanted to let her know that if she was going to take that many that there we're no other  snacks in the house for this upcoming weekend when she gets here on Friday. You would've thought I was telling her she could only take six pretzels to school with her with the way DH looked at me. Oh and how about the fact she was packing stuff for her lunch even though she was going home last night to sleep there at her mothers and could have packed herschool lunch over there instead of taking  our food!