Child Support and Trying to Keep LC

How do you get a narc to stay honest with their support while staying LC at the same time?

Unfortunately, I have 2 children with my xnh. Per our divorce agreement, he is supposed to pay a certain amount in child support and expenses toward our house that I'm so desperately trying to sell. He will shortchange the child support payments for various reasons. This last time that he did it I called him on it and he launched into a verbal vomit of a text message making me feel guilty for having other men in "our" house, that he still loved me and if I hadn't hurt him so badly he wouldn't have had to divorce me etc. Basically a bunch of emotional manipulation. This causes me to back off. Precisely what he is looking for so he doesn't need to pay on his obligations. I could get my lawyer involved but I don't think it would be worth it financially. How do you deal with situations like this? Do I just cut my losses and try to stick with minimal contact even though he's making out with a few hundred dollars here and there? His emotional manipulation makes me mad but it never makes me want to go back to him.