how Can I best move through it?

By moving OUT of it.

Well, yes. What she ^^^ said.

To flesh that out a bit, it will be extremely difficult for your bf to change.

You can calmly tell him the way things currently are are not working for you. Not giving him an ultimatum, just explaining how very serious the situation is. It's just possible that he will realize his future lies ahead, not backwards and step up.

It's also possible he will get weak-kneed and beg or grovel but not make real change and then you can leave with a clear sense you have no other option.

Things won't change. I lived it for over four years. Wish I had better news for you.

I think it's really hard for people to change if they're in a certain pattern of dealing with someone. They've been doing it for years, long before you came along and even though he's no longer with her (probably in part because she's pushy), his personality isn't going to change towards her or for you. He is who is. And that means that, after 3 years, things are going to continue as they have. It sounds like you're a bystander if he's not standing up for you. Was his mother like that too? Perhaps he tried to choose differently with you but old habits die hard. Since she is the dominant personality or the one established as that, doesn't sound like much will be changing because...nobody is changing. So you might want to consider changing. I agree with the others. You've had plenty of time and a front row seat to all this. Nothing's improving nor do you have any evidence that it ever will. You're young. You can start over with someone without all this baggage. Hard to think about when you're in love, I know. And so much easier said than done. But honestly ask yourself if you want to be writing about this for the next year, two, five, a lifetime of feeling frustrated and for what? I feel for you. I wish you didn't have to put up with this and I hope you'll find the answers you need after looking at the situation as it is right now and how it's highly likely to be...forever. Not trying to bum you out but not many of us here have great experiences with the SO exes or their kids or we wouldn't be here.

I guess it might help to have a few specific examples to know what he is "bowing down" to with her.

In general, it seems that a guy that has to give in to every demand his EX/BM makes is going to end up making his current SO miserable. Who wants a vindictive EX playing games that may even be done just to aggravate the new woman in his life?

I guess there sometimes can be the issue of the guy is afraid if they don't give in that the EX will drag them through expensive court battles.

Like the EX who asks for gas money when she meets for a kid drop off (my DH's EX did). Should he have to pay her? No, of course not. However, if he didn't then she would make some excuse that she couldn't let him take the girls. I know he could have taken her to court, but honestly, the occasional 20 dollar bill is cheaper than ANY lawyer right? So, it's kind of blackmail because they know that it is easier and less costly to milk the guys on small things knowing that they don't want to go back through court.

Now, there were times he said no too.. like when she asked him for money for christmas or birthday presents to put under HER tree. He didn't go for that and told her she didn't have to buy her children's love:)

A father being a ball-less wonder is never in a kid's best interests.

You're the other woman. Run and run fast!! Nothing here but heartbreak for you.