This is what I had to do with my off the track 3yr old TB, he was a runner, he would have hit the Derby if he hadn't busted his knee, my brother thought he was a cow poke so he rode his out... ah- put to much pressure on him. At this time I was say 14 & stupid- so I started to ride him when no one was home. I put him in a small pen (round pen, pasture, anything small & hard for the horse to get up to speed in) & worked him on stopping, turning.
I never did get him trained & have the scars & bones to prove it but its because of my age & how fudged that horse was.
Your horse seems so very much like Khanner, he is a one owner horse. That may or may not be the case but things should start over for him.
Good luck! Don't give up on him!