His follow through is good and overall his motion is smooth and flows well. He's got several energy leaks that he'll probably plug as he matures. Some things to take a look at for the future:
1) Use the lift to also gain ground toward home plate. If he does this, he won't dip so low as he comes out of the lift.
2) While that dip and drive looks like he's gaining energy, he's really just exchanging energy and not gaining anything from it. If he can get his hips out, he won't be able to collapse the back knee and that problem will almost eliminate itself.
3) His timing from top of lift to cocked position a bit rushed. While he works to get his hips forward, try to have him delay his hand break. Challenge him to hold his hands together for as long as possible, then break them aggressively.
4) His front shoulder is opening a touch early and is sacrificing torque. He looks to have about 135 degrees of external rotation because he's carrying the ball by about a foot before the throwing shoulder begins to come around. If the ball was still back approximately over the posting ankle, he'd have close to 170 degrees external rotation and much more upper body torque.
5) He's releasing the ball near his head (throwing from the elbow and not from the extended arm). Make full use of throwing arm length.
Don't get me wrong, he's off to a good start! I'd work on the hips first and see how that changes everything else. Then move on to the next step that needs work.