Thanks everyone for their input! It's much appreciated. I was a little upset when I wrote this, so I didn't make a few things clear. His top line has been building up rapidly since I saw the saddle fitter two months ago- he's literally gone up two gullets. He also hasn't bucked since then, but I am still wary of trusting him because of past incidents. As for pain, he probably is, but I've been working on it with lots and lots of massages the saddle fitter told me to do, and regular stretches, and there's been definite improvements, too. His walk is much longer and faster which I have been told is a good sign that he's losing some of his pain.
Also: I do enjoy riding him when he's being good, which he has for months now. I think I might give it a few more months and then look over our situation again. Who knows, things might have changed.
+ btw I still do lessons guys so hopefully my riding will improve too ((: