What role does your mother play, since it's her house? She could have him thrown out. Where is he getting the money to spend on alcohol (instead of paying rent, working, etc.). If your mother is giving him money or otherwise helping him, I would ask for the same in kind and see if I couldn't find a more comfortable place to live or make sure I avoided him however I could (sleep at a time he's not home and be out when he is or move my room so it's not as near his (so he doesn't think of me as much)).

Do you not know any rehab friends you could bunk with while you find another job and/or are you not still part of a group that might be able to give you local/concrete help? It sounds like your own situation should be taking the bulk of your attention, not your brother's, sounds like he hasn't changed a whole lot if he's never moved out, etc.