Sorry about all the drama. What did OW say when you showed up at her door?
The truth is, you DO deserve better. And brain injury/PTSD/depression or not, a better man would not behave this way.
Sadly, he may never be the man he was again. Or maybe he wasn't ever that man in the first place.
You're young, you don't have kids with him.....if I were you, I'd ride out these last few months until you hit that ten year mark, then I'd move on. You've offered love, help and forgiveness - sometimes you just can't make the horse drink.
Take care of yourself, let her worry about him for a change. And if his family doesn't know what's going on, tell them so THEY can take over worrying about him.