The thing that struck me first was that you are moving a little too deliberately. A little too smooth. A little too slow. You move up with your leg lift, you come down, pause just a little, and then move back out into your stride. You need to accelerate and build speed through your stride.
1- leg lift- you get into the conventional straight up and balanced position. When your lift leg has decended, look at your position. You have not even moved toward the target. If you look at it in slow mo, you have lifted the leg and basically returned to your initial starting position and not moved forward. You need to come up, close off the lift leg, and get your hip moving to the target before the peak of your leg lift.
2- I think you do a good job of keeping your front leg closed. The problem is that because of #1 you haven’t moved far down the mound and you begin to reach with the front leg. You also need to activate your rear leg and push off the rubber to get down the mound.
3- At front foot landing I don’t see much separation. Both your hips and shoulder are closed. When you throw the ball they are moving together in unison. Post a side view for a better look at this.
4- You have good external rotation. You brace up the front leg well. You pronate well. And you have a good follow through.
5- When I look at your back leg at follow through it confirms a few of my earlier comments. There is very little “reaction”. What I mean, is that when a pitcher accelerates well through his stride and then his front foot lands and the leg braces up- the back leg flies up in reaction to the momentum created. This doesn’t happen with you as much. It usually mean that you are holding back. You are not accelerating as fast as you can through the stride into front foot landing.
You have good size and lots of athleticism, so use it to your advantage!
I would suggest you consider two things:
1- Alter your current leg lift.
2- Work on using your drive leg more aggressively.
This will help you to accelerate, get you better separation, and improve your velocity. But, you seem to have really solid mechanics and you don’t need to tinker on too many things.