I have an older sister and we constantly fight, but we were taught to ignore a problem until it blows over. Don't do that. This is serious. I would tell your parents everything and sit down and make sure he understands that you love him and that you don't judge him, but that this addiction can destroy his life.
Don't allow it to get physical. Walk away before that happens, but make him see that you DO love and that he means so much to you.
Most kids that age act out when they feel abandoned or don't get enough love and attention.
That is what I would do, but I don't really know your family. I hope whatever you decide to do works out!
Good luck!