I would think your son would have issues with both high and inside and low and away misses. In the top link Will pitching #2 you can see that he lands with his foot open towards the first base side and his front knee also open to that side and not so firm. If you were to have him positioned so the concrete seam went through the middle of his back foot then his front foot should land very close to on top of the seam and pointed at the target or even slightly towards the right handed batters box.
To begin to better develop his direction you might have him reduce the leg lift and focus on driving to the target with his right hip. I believe his current leg swing into foot plant may exacerbate the front foot misalignment. He needs to develop more drive in any event.
Like Termhm I think he could use a firmer glove side, although I do not recommend pulling with it at this point. I suspect that if he begins to pull with it before he has learned to establish direction it will promote early shoulder rotation.
To be clear I would establish direction through hip drive and firm glove side and them proceed from there.
Best of luck,