My heart breaks for you and I wish there were anything any of us could truly do to help.
If I were to say anything, it would be to suggest an alternate viewpoint of your summary of your relationship with your brother ("I lost. They won.")
Maybe your brother won - for a while - because of all you did for him. Maybe he survived to the point of gaining strength and forgetting his abuse because in his most vulnerable moments he had you to rely on. And when he got stronger... he wasn't there for you. But he still achieved what he did because of you. Think of the lives he touched - the lives he created. Your compassion may well have guided him towards that point.
You are like the Giving Tree: sharing with and nurturing a boy, and rejoicing when the boy played with you and appreciated you back. And as time went on, the tree kept giving more and more - losing more and more of itself, plucked and whittled away - all to give the boy a chance to build a completely different life of his own, far away, taking from the tree and benefiting, thriving in his own way because of what he'd been given, even as he never said so much as a thank-you. To the Giving Tree, just knowing it had contributed to the boys life was all it needed, as what was left of itself was ignored. The boy had his chance at life, and the tree was happy.
Maybe when the shock and grief and horror and unfairness of it all have faded - and they will someday, somehow - you'll look back on how your gifts to your brother made his life endurable, even if it was a life he would not share with you. And like the Giving Tree, you'd know the life you made possible for him, and you'd be happy.
"Don't think it hasn't been a little slice of heaven just because it hasn't!" --Bugs Bunny