I agree wholeheartedly with the other posters who recommended calling in a specialist. Get some x-rays done, and have a chiropractor out. He really does look off somewhere.
I know you've been having trouble with getting weight on him, too... I know how frustrating it can be to have a horse that as soon as you fix one issue, another crops up. Some days I call Smoke "99 problems". Heh.
But, the best thing your boy has going for him is your love and attentive care. You will do what is best for him, I am sure of that.