I think you have made progress at the trot, definitely.
There is still a lot of worry on his part , regarding the bit, and too much activity there on your part, but I see longer periods where he finds the sweet spot and you give him a steadier hand, and he seems to realize that things could be good there.
I agree that a lot more work at a walk where he finds that sweet spot, you get him accepting of the bit AND walking forward, and then give him a long rein and get him to stretch forward, then slowly pick him back up. When you can do that with him neither speeding up when you give him a longer rein, nor tensing up when you take back up the contact, that will be a big improvement. IT's kind of "accordianing" your horse.
At the canter, I appreciated that you got up and off his back and you rode him forward long enough that he started to lower his head. However, there was a whole long time where he went giraffing around, building up that neck muscle and learning to lean and fight the bit, and you responded by pulling downward with both hands.
Better might be to use a lot more of ONE rein work, rather than both. If you can get lateral flexion, the horse will find it impossible to giraff his neck. When he speeds up, use the inside rein to make the circles much smaller. Don't panic, don't one rein stop him, just start him into a smaller circle. When he softens in the jaw and bends a bit, allow him to come back out on the larger circle (do this at trot). Use bending, one rein, and circles to slow him rather than clamping down with equal , downward pressure on the reins.