Hugs to Junebug, I did read it twice just in case the server was telling me something, lol.
You touched on a couple of good points, and that is regarding it being frustrating for him, which it certainly is, and that it shows I care and am willing/trying to help, even if I'm not that successful.
I can see how it's just grinding him down day after day, even though I don't see him every day, but I can pick it up from his e-mails. He's been living with this for more than 20 years now and he's worn out in every way possible. The fact that I represented some hope but nothing concrete has happened is no doubt disappointing. I realize that, but there's not much I can do other than to keep trying.
I think the pushing away is classic PTSD. I've done it myself, when I was suffering it more than I currently am, and I can see him doing it now. The one thing I've told him is that he can push all he wants, I'm not abandoning him. No matter how "unlovable" he might be acting, I'm going to chalk it up to the PTSD and remember there's a wonderful man under there somewhere. That's what I would want someone to do for me.
If love is supposed to be "unconditional" it means we love the other person no matter what conditions are operating for them at the time. We love their inner core, their spirit, their mind, their soul, not just their physical appearance or their ability to tell funny jokes. We do love them "for better or worse", and even though PTSD is pretty good at showing us the worst, we know that they are not defined by their disorder.
Granted, as much as we love them, sometimes it's just not the right thing to be around them. That's the hardest part of all -- knowing when to put some distance between you.