Your bf abused your son and abuses you. Cutting his son's ear and not letting you take him to the er is insane. Your poor son. And the things you describe that he's done to you... oh my gosh-- my heart breaks for you.
Please please call a dv hotline and get a restraining order and get away from him. I really truly know the feeling of taking someone back and wanting someone back for the wrong reasons... You are wise to know that about yourself and brave to be able to see and say it aloud...
I am so sorry for all you are going through and for all that has happened to you and your kids.