Damn, dude, thats awful. I think you should tell someone (Not your incompetent teachers) who has a position of authority. And get them on your side. Basically, dont troll him on facebook, dont put laxatives in his food (unless you really want to.) Get as many people on your side as possible. Then you'll have him and his goons outnumbered. Bonus points if you have an adult in an authority position on your side.
Best of luck to you.