Honestly, part of Monster's jumping problems are probably that if you didn't do extensive ground pole work before making any sort of jump, its scary and he isn't quite sure about the whole thing, especially being off the track, and not used to having to work over any sort of obstacles. As for retraining him, a lot of it, is just going over the basics, walking, and trotting especially, and working on transitions. If you like him that much, I wouldn't give up on him. I love ottb's, and they have so much potential in them. Most of the one's I've worked with did absolutely fine with a few months of very light easy work, and destressing from the track atmosphere. I would work him over trot poles, and eventually canter poles before putting a fence in front of him, and see if he doesn't take to jumping with that approach.