My pitching mechanics

I think your mechanics are going to limit your ability to add velo and deception. IMO I would get a new pitching instructor, or work on emulating what the best pitchers do.

1. increase tempo
2. rotate toward deep short/third baseman with your lead shoulder and knee. Hips will open into footplant, well ahead of the shoulders.
3. make an effort to lead down the mound with your back left pocket
4. try to break your hands behind your lift leg (it will help with number 2)

Im not trying to pick on you or your instructor, but I feel your capable of a lot more. Much like hitting, pitchers need to load and unload while getting a running start. What does your instructor emphasize with you?

I think your basics are fine. You are obviously doing this in slow motion to perfect the things you have been taught. I agree with that.
It is better for some to do as Deemax says if you are ready to make an adjustment. My son learned the basics similar to what youre learning. The only thing different was he stayed back longer and let his lift leg drop straight down and then slide out to plant. I know the one college coach got him to rotate his hip and that changes how his lift foot comes forward. More of a sweeping motion and the jury is still out on wether it is better for him.