Lungeing is not just for getting energy out. Lunge with the purpose of getting his attention, making him focus on you. Move his front legs, back legs, make him walk, trot, walk, canter, reverse, keep mixing it up so he is looking to you to see what’s next and not focused on everything else. This works wonders with my OTTB. Do the same thing when you ride. Make sure he is focused on you. I even make little “chh chh” noises to get his attention sometimes, and keep mixing up the exercises.