Controlled by ex spouse

I don’t know how to prove my soon to be ex abuser husband is controlling me(trying to) , I left him awhile ago he’s bitter,& If I don’t do what he wants he won’t cooperate with divorce or getting custody figured for our child. I won’t give him the SSI to file our child bc he doesn’t do anything & his mom already tried to get his social for a credit card she’s known for that, so he won’t sign divorce papers and cut him off of insurance , He talks about his own child saying he doesn’t care and I want to get sole custody and just get away from him but he says he will fight and win bc I have no proof, he won’t text things only calls. Even with abuse he made sure I had no bruises and would take my phone so I couldn’t record&threaten me. The apps i’ve found all use fake numbers and he knows what i’m doing by calling from those, he won’t talk on speaker phone and I don’t know how to record on iphone without him knowing, screen record with audio didn’t work. Can anyone help? I just want to get rid of the POS move and have a good life with my child. I’m scared to he will get 50/50 custody even though he doesn’t want it & mistreat our child. I can’t prove his mental illness bc he goes to therapy not for real help just so I cant use it against him. I thought I left abuse but He’s still getting away with a different type of abuse and sadly a lot always do smh. I have contacted people for help and it’s always I need proof which I can’t get. Anyone know how to secretory record? It’s legal in my state. Maybe I have to stay married & live my life separately so he can’t get any custody. I can’t afford a lawyer and even if i’m scared I will lose with no proof