Blair,
I've been following your story and regret all that you're dealing with. To live with the pain, disappointment, apprehension and outright fear, all of which are very real, is difficult enough without having an unsupportive family member to put up with. Physical violence is a whole other story. Aside from the obvious hostility, the fact that he kicked you in your back and then again while you were lying down is representative of something else.
The first thing that comes to mind is substance abuse. Barring that, I'm in complete favor of castration which would inhibit his natural testosteronal aggresive tendancies.
Another way to deal with him is legally as Laura suggested but sometimes it's difficult to press charges against family members. No... I think you should cut off the bastard's balls!
Also, if you're still able to, you might try kicking him back. A directed, well placed kick serves so many purposes, don't you think? (not that I believe in fighting violence with violence, but really, is a testicular kick violence?)
On a more serious note, no one EVER deserves this type of physical abuse and I agree, removing yourself from a bad situation, even if it means distancing yourself from your brother, is in your best interests at this time. Surrounding yourself with caring, supportive people will do much more for your mental state than your realize.
I wish you well, Dale
Mark, if you need to edit this post, I understand.