Idk how to breakup with my sons father

The last 3 years has been full of up and downs, but the down moments are just too much for me. I know that i just want to be done, we are both toxic for each other and weve both done horrible things to each other. He is abusive in every way tho. I moved out of our apartment 3 weeks ago after things turned physical and he hit me several times because i wouldnt "shut my mouth" meanwhile he wont stop talking shit to me but expects me to just sit there and not defend myself. I called the cops and even with bruises all over my face they didnt arrest him. I left but he wouldnt let me take our son and the cops couldnt do anything about it. I have a history of abusing prescription drugs that i no longer take and havent taken since I found out i was pregnant with our son in April of 2019 but thats why he doesnt "trust me". I made alot of mistakes in the past with my older 2 children, but im not that same person anymore. Ive been clean off of the meds i was taking for over a year and a half, kept the same job for over a year while he hasnt worked a job the intire time weve been together. I have no friends, but he has several and has already coached them to say horrible untrue things about me if i tried to take him to court or press charges. And even through all this he still wants me back. Has begged me to come back and ive tried telling him so many times that I dont want to fix us and that we both just deserve peace but he's obsessive over me. The moment i tell him i just want to be done he tells me im a shit mom and our son is better off without me and says i cant see him anymore.. So I end up saying ok we can work on things. I go visit them everyday and havr to pretend like I still want this. Idk what to do. All I do is cry, I feel trapped and like im in a very dangerous situation. Just please give me some idea of what to say to him. Ive tried telling him we can just be friends still but thats not good enough. Please help me. I feel broken and like im trapped and theres no way out. He will do everything he can to make my life hell.