I agree with looking at your agreements and if she is falling short of her end...either go after the child support and what is rightly yours, or let the child support go for now (can't get blood from a rock) and hang on to all your stuff, she already got her share.
You are doing a good job, you take good care of yourself and your kids. She shouldn't be allowed to disrupt your lives and at some point should be help accountable for her neglect.
Big hugs because I know this is hard.