The only problem we had today was that he spooked at a random tire that someone left out in a wide open space. I knew he was testing me over it because none of the other horses spooked at it. When we tried to pass it he would snort and blow and try to back away or run forward so I side-passed him over to it and walked around and past it several times and then side-passed him so that he was standing over it. I then rewarded him when he relaxed and let out his breath. I didn't have a problem after that!
But I am so proud, he's finally got all of his weight back and now is getting muscle on his hindquarters. After my lesson last Tuesday I even led my little brother around on him.