Obviously, this is a bad situation and I hate that you are stuck in the middle of it. However, to be honest with you, I really don't blame your brother at all for what he did. If it had been me, I probably would have done the same. I'm sure your brother understands that you love this guy, but you have to realize that your brother loves you too. This is why he done what he did. He was only protecting you and the rest of his family. In his mind, he was probaly thinking that if your boyfriend could knock down your parents door to their house, there's no telling what else he could/would do. Therefore, your brother had to put the fear of god in your boyfriend to make him realize that if he did anything to hurt you or anyone else in his family, he would be there to "get" him. Do you see what I mean? I know fighting isn't the answer to all problems, but sometimes that's the only way some people know how to handle certain situations. Especially, when it involves the ones that you love the most and you want to protect them. If I were you, I would give this relationship a break for awhile. See if your boyfriend is really what you want right now. You may find out later on down the road that you may be happier without him. Love is not supposed to hurt. So, if it does, something isn't right with that relationship. It usually only gets worst unfortunately. Just try to be a little understanding to why your brother done what he did. I'm sure he was only trying to do what he felt was the right thing to do at that time.
Good luck to you and your family!!!