I like a lot of what you have going on, such as your drive off the mound and your force production and arm action, but I think something is off with your spine angle. I would need a true side view to comment. I think your position on the rubber combined with your stride direction and open front foot landing is impacting your upper body balance. It looks like only your toes are actually in contact with the rubber and you are striding to the middle of the rubber. For your delivery, you may need to move more toward the middle of the rubber and stride to the same spot.
More video of jack his velocity has plateaued at 78 even though he has been working out with a personal training for 3 months