How do I leave?

Today was the last straw for me. Normally no matter what we’ve been going through during the week Sunday’s are good days for us. We normally go to a lake or the beach or something and just relax and get food. But today was terrible. all day we argued and things got so bad he grabbed my arm as hard as he could leaving bruises immediately. He grabbed me while I was holding our 2 month old son and the baby started crying so hard he wouldn’t let me walk past him and I told him I just wanted to leave and to let me go. He called the cops and said I was kidnapping our son but I just drove off I had to get away. Then stupidly I went back an hour later but then he was drunk and one second he was acting friendly the next second he was pissed at me. He’s outside right now drinking even though he has work in 3 hours he has missed so much work lately and is now going to be fired if he doesn’t go tonight which he won’t be... I’m just done but I don’t know how to leave .. I can’t afford to move out. I could move into my parents house but that would literally be hell and I wouldn’t be able to take my dog. I don’t know what to do I feel trapped.