Get strong and take every legal means necessary to get this monster out of your life. Evict him. Get a restraining order. Change your locks. Call the police if he shows up on your property. He has shown zero compassion for you. Show no compassion for him.
You must protect yourself and your son. I think he has beaten you down to the point that you no longer value yourself. The stronger you get, the more action you take, you'll become more and more powerful and regain your self respect.
Kick this jackass to the curb.