Quoting speaktruth2powr:" Don't allow him to have the child until there is a custody agreement. Without one, he doesn't have to give the child back to you."
This is very important to remember. If he takes the child and does not return at all he is not kidnapping since he is the father and there is no custody order in place. I'd get to talking to a lawyer about custody.
Also, get a restraining order against the jerk who put you in a choke hold. It's hurting your bf? Tough smurf. It should hurt your BF that his brother assaulted you
, and he, more than anyone, should be trying to protect you.
You need to think about yourself and your child more than your boyfriend right now (that's hard to do in reality sometimes). Listen to your mom, ask her to help you get in touch with a lawyer and remember to thank her for being there for you.