I think it's great that you are so highly motivated to delve deeply into pitching mechanics issues that many pitchers never consider, no matter how long (or short) they play.
In all sincerity, I think you are doing yourself a disservice at some level by trying to learn everything you need to know via the internet. If you were getting high-quality hands-on coaching and mentoring from a truly knowledgeable pitching coach--one who would take the time to look carefully at the mechanics, sequencing, and timing of your pitching motion and who would then help you to create a priority list of things for you to work on, and help you with the specific drills and conditioning work you need to accomplish your goals...you'd be far ahead of the game right now.
I'm sure you are getting some coaching from somewhere, but I'm not so sure you are getting quality help with all of the many excellent questions you raise. Please don't misunderstand me, I think the advice you are getting at this forum is generally of very high quality. If it helps steer your thinking in directions that are useful to you, then that is about as much as you can expect.
However, at some point--and I personally think you've probably arrived at that point--you need to supplement the written advice you are getting here with live, hands-on coaching from somebody whose authority and ability with the subject you can trust.
About 5 years ago I knew as much about pitching mechanics as I knew about quantum mechanics. I still don't know very much about quantum mechanics, but my son became interested in pitching so I set out to learn as much as I could about the subject--at 8 to 9 years old he certainly was not going to be able to read and comprehend the mountains of written literature on pitching mechanics...the boy just wanted to throw the ball at that age, so I felt it was my responsibility to find out if there were optimal and healthy ways that he should do that. Over about a year's time I bought and read more than 25 books on pitching...what this did more than anything was (1) allowed me to develop a pretty good B.S-meter so that I could tell pretty well whether someone knew what they were talking about (or just making it up) regardless of the inevitable differences in jargon that people use and, (2) led me to seek out the very best personal coaching and mentoring that I could find for my son.
In my personal case, this little odyssey led my son and me directly to Tom House and the NPA. Tom wrote about 10 out of the 25 books that I scoured for information and I became convinced that here was a guy who had devoted his professional life to deep learning and optimization of his approach to coaching baseball pitchers. When I finally went to the Baseball Hall of Fame website and listened to Nolan Ryan's induction speech, wherein Mr. Ryan spent 3 or 4 minutes specifically acknowledging Tom House's outstanding influence on his later career, I was convinced--if at all possible, my son would get hands-on training from this same coach.
Imagine my delight at finding out how easy that actually is...Tom and his NPA organization offer a great variety of hands-on clinics for pitchers in San Diego and all over the country. Since we started going to these clinics about 4 years ago, I've always felt that we received far more value than we paid for. But, of course, different people may think very differently about how they like to spend their money. Personally, our next pitching clinic vacation in San Diego is a much higher priority for us than saving up for a boat or a motorcycle or a...you name it.
Tom House is undoubtedly not the answer for everyone--but maybe one of the many, many coaches who have earned NPA certification directly from Tom is the answer for you. Or maybe not, that's your decision and no one elses.
Not knowing what part of the country you live in, I'd suggest that you look at http://www.nationalpitching.net/memberhome.asp?xu=101883&ct=2&cft=wb&sid=37A7AFF8-EF3C-475B-85BC-3E88B5301D5F , find the "Coaches" page, and at the bottom click on the link that helps you "find an NPA certified coach near you". There are at least 200 NPA certified coaches around the country and most of them are very, very good. You can even contact the NPA directly for detailed information about which of their coaches in your area they would recommend most highly to you.