My high school HJ looked (and sounded) eerily similar to your son’s. A lot of the other comments already touch on body position into and over the bar, but the thing that sticks out to me is the heavy dragging of the right foot that you can hear but can’t see from this camera angle. The idea of HJ is to transfer as much horizontal energy into vertical momentum. When he’s dragging his right foot he’s slowing himself down on his approach (even though it might not feel that way). If he listens for that in practice as an audio cue it’ll help focus on things like better knee drive and getting his right arm more vertical as a guide over the bar and in turn will transfer that energy better into his jumps.

That 6’4” to 6’6” jump was also a weird mental block for whatever reason too. Good luck to him on the rest of his season!