I think the playing is fine; the main issue has already been pointed out in the ornaments. I think the problem is that his ornament is coming in slightly before the beat when all baroque ornaments should come in on the beat, this causes him to try and "catch up" with the left hand to get back on rhythm which is where the herky-jerky feel is coming from.
As far as body movements are concerned, I don't mind them as long as they are natural and don't affect the playing. Some kids think it's cool to move or that you have to move, that I find to be a problem. I do not like elbow movements, it's a misconception of relaxation. Once the elbow dictates the movement or rotation of the wrist, that is a problem. This of course is coming from an individual who worships Glenn Gould and detests Lang Lang. Movements didn't seem to be an issue with your son, so most of this is useless information (my forte).
Keep up the good work, and above all, enjoy making music.
Best wishes,