Custody/mediation

I broke up with my boyfriend because he is mentally, verbally and physically abusive. He’s very verbally abusive to his 5 year old son although he denies that. But last I knew telling your child at 2,3,4,5 years old to shut up, calling them retarded, saying “what the hell/what the fuck dude” to them, is verbally abusive to a small child. He’s hit me, dragged me by my hair, chocked me, scratched my face up. We have a 15 month old son together that he’s hardly helped me with, I was a SAHM for 10 months so my mom and my grandma helped me with a lot of my son’s expenses like diapers, clothes, wipes, toys, formula, etc. he’s helped out a hand full of times. Now since I’ve been working, I’m taking care of him and his expenses. I don’t want my son growing up thinking that kind of behavior is okay. He’s going to court with his ex to see where their son will be going to school since they live in different states. And once I leave the house he’ll no doubt take me to court too, although I’d rather do mediation. I can’t stand the thought of a complete stranger who doesn’t know anything about our lives, make the decision about what happens with my son. I want to make sure I have all my ducks in a row when the time comes, I want to bring a lot of documentation to prove he didn’t pay for our son. Oh, on top of everything he currently has no job. Any tips??