What should I do about my father?

Just talk to your dad when the two of you are alone. Everyone makes mistakes, but at least your brother has a chance to fix them. And wants to fix them. He needs all the support he can get right now. I know how disappointed your father must feel but anger and violence is not the answer. Don't speak out when he's in a fit of rage, it won't do any good. Tell your brother to stay out of his way. That's the best advice i can give. Your father needs to find forgiveness in his heart, after all, your brother is his child.