Could you address the specifics of the youngster in the video, step by step in his video of where your advice pertains, movement by movement, frame by frame of him, so he can learn from your advice, and your observations of others less knowledgeable than yourself.
In other words, take your comments, all of them, with respect to good form and movement, and point out what, and what not, this youngster is doing.
Take that advice of yours, use the youngster’s frame, by frame motion, and point out your instruction so he and his dad can benefit specifically, when an d where it will help them the most.
I am adding 3 slow motion pitches, I think Evan has made some nice mechanical adjustments in the last three weeks. Not landing as closed, not crossing the body as much, moving sideways more and not falling off towards first as much, better glove action and getting out front more.
I thing he still needs to stay back longer and get more push off the rubber and have a faster arm.
Your son is adjusting to the suggestions that you received here - it looks like. I’m not a mechanics coach, far from it. However, I would like to suggest that you allow your son to “fit in” and absorb what he now doing. To your credit, you’ve passed on advice, and to your son’s credit, he seems to be doing nicely. So, one step at a time and give your son the time to examine what is show above in the video, think through what he’s looking at, and what he thinks is his strong points and what are his weak points.
Now here’s the tough part dad - take a step back and let your boy figure this out. Here’s a hint to his movements during this release: the body has weight issues while in motion, either forward or sideways, the body has to balance itself. This balancing act is the body’s natural defense mechanism for protecting itself from falling and other particulars. So, ask your son to pay particular attention to his glove side of his body while going down the mound and his glove side in its entirety during and after release. Suggest this, then step back and let him work things out. If your boy is ever going to progress and develop, be competitive and worth watching, he’s got to figure this stuff out for himself.