Seems like a really scary environment to be in, definitely not good for anyone; I feel like if he's being so abusive, your mom should really consider divorce and moving away from him because if he has only been causing trouble/arguments/fighting he doesn't seem fir to raise you/your brother. I feel like if you're unable to find staff at school to help you out (didn't know you were only 14 O.o), that maybe since your brother is in college, he can help you and your mom get out of this situation by seeking advice/help from the staff on his campus or at least find people that might have connections to the appropriate places you need to get in touch with.
If this has been going on for a while don't suffer if it can be fixed. Best of luck dude D:.