You're correct - the pitcher in the first picture does not appear to have started his shoulder rotation. I believe the throwing arm is behind the head because the pitcher has preloaded his scap and his flexibility allows/requires that much abduction. In my opinion, you want to delay shoulder rotation long enough to achieve maximum hip and shoulder separation. In other words, you want to give the hips time to fully rotate before the shoulders rotate.
Again, my opinion is that the speed of hip rotation IS important and faster is better than slower.
I am not familiar with him so I can't comment.
I believe there is a push off at the beginning of the delivery. This early push is what initiates momentum. But I don't believe there is a big push later in the delivery.
These are not stupid questions - they're good questions. And don't your grammar isn't that bad either.