Your pivot foot seems to be in a hole - in front of the rubber. So, here's an absolute about pitching:
--- starting off with your main balance/ momentum stabilizer in a hole, starts you off IN THE HOLE.
Anything that follows is going to go down hill from there. ----
Also, because your pivot foot is in a hole, your toe is pointing downward, which will force your weight slightly off towards the third base line, initially.
Then, as you drive forward your body's balancing mechanism(s) go to work by OVER CORRECTING. Hence your now throwing accross yourself. Take a closer look at your video an what I alluded to just now. The final proof of the pudding is your stride foot pointing off to the first base line when you land and -- if you look closely, your stride foot actually grinds sideways -- again towards the first base line.
Level off the surface in front of the rubber, seeing how you prefer that style as appose to the :: step-back-rock, which is mostly impossible on most public and private diamonds.
Then I would suggest adjusting your feel to this level surface condition by first using a gentle leg lift - no higher then a foot off the ground as you turn, then sweep your stride foot -about six inches accross the mounds surface, just to get the feel of your controlled shift in weight driving towards home (target). Concentrate on planting your stride FOOT squarely at your target- not off towards the first base line. Concentrate, concentrate, concentrate on this fundamental stride foot discipline.
You'll find that staying more upright during you stride - at first, gonig slow and easy does it, will sooner or later give you time to adjust to what's needed to correct what you have been doing.
Mind you, this is just a starting point - not an end in itself. Practice and concentrate on your own, in front of a mirror - floor length if you have one. At the same time, reinforce your muscle memory to this posture.
it's that important. Why? If you continue with this stride posture that you posted on your video, your forcing your stride leg/knee with loads it was not designed to support. In addition, your now probably experiencing stiffness in the base of the neck and lower back - if not in the near future, if you continue. And by the way, try and focus on the catcher's mask as a target while you settling in with this discipline. This tageting point allows you to be a bit higher in your flight path of the ball and will help you ease the transition process.
Overall though, you seem to have great punch to your delivery. Simply work on the above - slow and easy does it and I guarantee you'll be a competitor with an awesome command of the hill.