Welcome!

you are in the right place.
There is a lot of tools and reading here on things we can do and things to stop doing. So I guess read as much as you can. Also, others here have a lot of experience, and can share their experience.
It's sad really to see how the black and white thinking can mess things up.
Especially when kids are involved.
I guess just do your best, take care of yourself. It's hard to not get sucked in to the dynamic. If I can be detached, I can be a buffer, I can make a difference.
To do these things I have to take care of my well being. I need at least one close friend I can share with who won't judge me. Who will just listen.
You care a lot and you will able to see a path. You will learn much here. Be patient with yourself.
Sincerely
juju