Wow, sadconfused - sorry you and your kid are in such a wretched situation.
Just want to echo that the ONLY WAY anything will change is if something changes, and likely it is going to be you who has to make the change. Sounds like you are on the precipice - good. Sometimes the devil you don't know is FAR FAR better than the devil you do know. That you have a kid to protect/raise/teach/nurture is a huge responsibility. I hope that you have the strength to continue to take steps forward, and away from this guy who thinks physical violence is acceptable.
PLEASE take care of yourself, and your child. ((hug)) You both deserve to be treated well!