I need to get away from my mom

My mom is beyond horrible and idk what to do. I'm 18 and I can't go anywhere... My mom has legal guardianship of me and my son. I got pregnant at 15 and my mom slapped the shit out of me and tried to drag me to get an abortion. My boyfriend's entire family is from El Salvador. They were illegal. We were both just teenagers. My mom became more abusive as time went on and would do things to provoke me. She would hit me and call me names and then say things about my son. And when I had enough and started acting "crazy" she would report it. She reported my boyfriend and got his whole family deported and I haven't heard from him in a year. My mom had a tone of videos of me saved acting crazy but cut out what she had done to provoke it. Like trying to hit me with her car.... She had her friends say I was mentally unstable and can't make my own decisions which is why she was awarded custody over me and my son. She has continued to abuse me and do so in front of my son. Last night I got home late from work and she was mad I didnt tell her I would be late. I ignores her and she put her hands around my throat and slammed me into a wall. My son was crying and she told him if he didn't stop she would cut his throat. I bit her and took my son in the car and locked the door.... She has a complete hold over me and idk how to get out. She knows I was bluffing about the lawyer because I can't afford it