Josh,
I'm really sorry to hear about your brother.
From what you've said, it seems like his problems are running rather deep and there may be little that you can do at this point to help him. Depression is a serious issue, and it may be better for your friend to return home for a while so that his family is in a position to care for him and, hopefully, help him seek professional help if necessary.
My advice would be to make sure that he knows that you and the rest of the chapter will support him, regardless of what decision he makes. Let him know that you will be there for him no matter how many miles separate you, and that if he does decide to return home for a while that he will always be welcomed back with open arms when/if he comes back to school. If he does leave, make sure that you stay in touch regularly so that he knows that you and the other brothers have him in your thoughts. A phone call can make a world of difference when you haven't seen someone in a while.
Good luck, and please keep us updated. I hope that things work out for him.