I'm going to make a few suggestions. Mind you this is more of a classical dressage approach. Do not put your hands on his whithers, raise them and just let your elbows hang at your side, hands up. This allows you to sit up and back while your hands still rock and follow much more loosely with Justin. Also, no see-sawing him to slow down. Lift up, not pull back in a give-take, pulling back and putting hands down will tilt your pelvis forward into a driving seat. If you sit back on your butt and lift your hands and body, you will sit deeper and help him off his forehand. Definitely lots of walk-canter-walk transitions, a few strides, not even a full circle. To ask for a walk, you should first give the reins, not haul him downwards, but teach him he can return to a nice forward walk. While cantering, loose rein, let him learn to carry himself for the short while that he is. Cantering round and round does nothing, transitions will teach him to rock back and pay attention, along with rewarding a non strung-out nutsy canter.

I would warm up with a lot of trot work, just on the buckle until he settles, and then work on some lateral work before beginning canter transitions.