I don't think op is entirely being honest. And I don't mean with us, I mean with herself.
I don't think it's that she doesn't like the kids. I think its that she has seen this other side of him and she doesn't like him, when they are around his kids.
Op has him there 9 nights in 14. Then the says where she should be able to relax spend more time with her children, he is pushing to be at hers with his kids. Op doesn't want that, but he has continued pushing. Deep down she knows this is because he doesn't want to parent them alone.
He was going to go for 50:50, why? Because it was in the best interest of the kids? Or because he thought op would be there to help him out more and he thinks that dad's who do 50:50 look better. If he thought 50:50 was in the best interests of the children, he would still be going for it.
So either he didn't really ever believe it was in their best interests and was only doing it, counting on op picking up the slack. Or he believes it is in their best interests, but is going to ignore that it's best for them in an attempt to keep op. Neither is a good dad.
I think op has seen him parent on a longer basis and not liked what she has seen. She has seen he is very much a Disney dad, that is pushing responsibility on to her and her teens. He expects her and her teens to put his kids first. To make life easier for him. I think op is projecting her dislike onto the kids.
In addition, the way op talks about his ex in a disparaging tone and about her partner being a walk over etc. This all has to come from ops dp. I think he sees his ex finding blending families far easier and is probably a bit jealous trying to push for op to do this.
Overall, I don't think this man is a great as op think he is and she is projecting that onto the kids, so she can keep their love story on a pedestal.
The more op writes, the more this man comes across as someone who only has his own interests first. But op putting him forward as 'he put the kids first and broke up with me' frames him as the good hero dad.
His anger will have been defensiveness. But not about his kids. If dp acted in a way that clearly showed, he disliked my kids he would be just gone. That's it. No negotiation, no scaling back plans I had, to have my kids more. I think his anger came from the fact that he had a vision in his head of what the future looked like. Which included him having his kids more, but not actually doing more because op would have picked up the extra.
Its ok saying op is t a step mum, she isn't. But that's where he saw this going. That's where his anger comes from. His plans, that he hasn't shared started falling apart and his reaction was anger at that.
Maybe they can maintain a relationship where they live apart. I doubt it, he is already trying to drop the 50:50 to get op back. Then when he does, he will start trying to get op to accept the kids more and more.
But, everyone is assuming that this will get better as his kids get older. But that's not a given. Infact having this dynamic as with teens where their dad gives in whenever they want something, is worse when they are teens and adults.
Wether staying separate can work is really dependent on what op wants from the relationship long term.
If she is wanting a relationship where they eventually live together/get married and have a completely shared life, she may end up staying (keeping things separate for now) only to find it was a waste of time. Be arsed his kids are in their 20s still stropping while he appeased them.
I can see op, staying with him and in 10 years regretting the decision, tbh. I just don't think she is being honest, he is the problem.