Yea definitely get some advice on that. If it’s a stand you can make then it does even the balance a bit, but will undoubtedly cause a backlash from him. He sounds like a good candidate for “grey rock” though - the type who enjoys causing drama. So the less drama he’s able to cause the better.
I know you don’t want his money as such, you want him to do the right thing by his DCs. But if he doesn’t, and you can get to a place where you don’t need him to, then the power balance returns to you, as you don’t need him, you don’t need any contact with him, and once the DCs are old enough they can manage their own relationship with him without you even needing to be involved. You can’t make him be a good dad, or do the right thing. So all you can do is step away from the conflict.
Imagine a life where they text him directly to confirm when he’s collecting, you kiss them and then busy yourself with something when they leave, so you don’t have to see him or speak to him, he rants about something and you don’t reply, as you owe him nothing.
Maybe have a look at the book called ‘I am the parent who stayed’ by an awesome MNer called Nina Farr. She was an absolute legend throughout her break up with her ex and beyond. She’s gone on to help other women dealing with high conflict exes. She’s great at helping you reset your expectations, and build your confidence to lead your family in your own way. Definitely worth a read.