Very nice looking horse. He seems a little bit stiff in his back, like he rushes around in a rapid trot without much swing in his back. Working him over some poles and low jumps like tht will be good for him. Neat horse!
He looks like a typical OTTB. Slow his gaits by slowing yours. Find a speed of trot that's acceptable and slower and post to it. If the horse speeds up, he'll get out of sync with your posting and will have to find his way again. In the canter, lock your seat down and don't give him the energy he wants. Be stable and make him come down to your speed.
He's a nice-looking horse though and looks like he enjoyed those jumps!