For some reason I thought he looked slightly off trotting in the second video. Jumping, you seem to come back to him a little fast, hitting his back. To fix this, try staying up in two point until all four of his feet are on the ground.
From the stills I can see in some of them, your butt isn't out of the saddle enough. YOu need to bring your hands forward and your chest down a little. It looks like you're leaning forward and supporting your weight on your hands. Also, your leg seems to have slipped back over the fences.
Under saddle, I give your form an A+. I really like how your shoulders are back, your arms and hands look great, and your leg is nice. Your leg wiggled a little bit in the videos, but I don't think that's anything bad.
Very nice riding overall. Horse has good potential, just get him even with his knees and he'll be stellar :)
“Have fun - Stay on top.”
"There's nothing like sixteen hands between your legs"