You’re trying to accommodate a self taught process with a self imposed learning experience that just won’t work. I’m not trying to down grade your sincerity or your hard work - but, you seem to have no experience or awareness of what you’re doing right, how and what the fundamentals of pitching are, so anything that’s suggested here is going to be a real problem.
Please don’t not take my observations in a negative way. What you need is someone that can be right there with you to show you step by step the fundamentals of pitching - fundamentals of body setup/balances through your pitching cycle, and the finish of your pitching cycle.
You’re trying very hard to throw the ball hard, and therein is a health problem for your arm/shoulders and groin muscles
So here’s what I suggest, ask around for an adult baseball team in your area, or a college club and go to a game and approach one of the pitchers after the game and ask that pitcher to show you the fundamentals of pitching. Nothing fancy like tossing a curve ball and stuff, just the fundamentals from the windup. Most guys would be flattered to be asked to help a youngster. Just don’t spend a lot of time there, only about 20 minutes or so.
Then take some video and from there, post if here and we can refine what you’ve been shown. This way, at least, you’ll have a base to work from and a better understanding of why.