Looks like you’ve got a fine young pitcher there.
I liked the quality of the video for analysis. Everybody should use a tripod like you did!
Here are some things you might want to think about:
The pitcher starts very tall, but drops down perhaps 8" - 10" very early in his stride forward. Tom House/NPA would say that dropping down abruptly is wasted motion and most likely occurs because the pitcher is not strong enough to maintain his original posture into foot-strike. Their ‘fix’ would be to ask the pitcher to start from a balanced posture that is already about as low as he gets in his stride. If he does that, then all of his motion will be directed forward (where it belongs).
The pitcher looks like he has been taught to “stop at the top”, i.e., complete his leg lift before initiating forward motion to the plate. However, think this through: If the pitcher has created no forward momentum by the top of his leg lift, he must then create forward momentum from a static position, balanced on one leg. Instead, House and the NPA would strongly recommend that this pitcher shift weight forward at his hips from the very beginning of his leg lift.
The pitcher has almost no drag line. That is most likely related to the high posture that he starts with. Even though he drops down considerably into his stride, it may not be enough to give him a drag line. You might want to experiment with height of starting posture with this pitcher until you get him low enough to have a stable, repeatable drag line.
The post foot’s drag line is (a) the post foot’s way of helping to stablilize the pitcher’s motion toward the target and, (b) a good diagnostic for direction of the pitcher’s momentum at release.
House/NPA suggest from their research that nearly all elite pitchers have a drag line that is equal in length to about 2x the pitcher’s shoe length.