Really think he needs to minimize the step to the side at the beginning of his delivery. That’s a lot of unnecessary movement in directions other than towards home plate. And that can lead to inconsistency.
Also needs to work on getting the hips moving toward home sooner while keep the front leg back/closed off a bit longer. Google “Hershiser Drill”.
Roger makes a good point about the large step to left. One thing I would say though is that you do a good job getting back to a fairly quiet but powerful leg lift even with the potential for a lot of inconsistency that the side step creates. I would minimize as well just because game situations tend to exaggerate our flaws and bad habits.
Your finish actually looks pretty good. To me the finish is always a symptom of movements earlier in the motion so that’s a good sign.
Two things to create more potential energy and arm whip. Exaggerate even more the start of the move down the mound with your left hip. This creates somewhat of a triangle between your post foot, front hip and head. Make sure you are still getting that good hip rotation and that you aren’t staying closed off and losing that nice linear move you make with your front leg currently. Also keep a quiet head and level-ish shoulders.
The second is just to break your hands and make sure you don’t get lazy with your glove arm. It starts to “fall” rather than drive to the mitt, although you correct it a bit later on. I like to teach that when we break our hands our thumbs go down to keep our elbows higher. This will also keep you more closed longer and build up that force that eventually turns to the “W” and then better arm speed.
Last thing is, you’re only 13. Your body will only get stronger from here. Looks like you’re tall and lanky (like me). Find someone who is an expert in teenage/high school strength training and focus on your core and legs. Core keeps the arm healthy and legs give you functional strength and velocity.
As always, if anyone disagrees with what I’m saying, I’d love to hear why. I’ve pitched all my life with little arm injury and solid control. Never lit up radar guns but consistently sat in the low to mid 80s. I’d like to think I know what I’m talking about, but please teach me too!