I'm a week late to this, heyman, but you're doing a great job. I particularly impressed by your spiders, ladders, and your scalpel picking is excellent. Most people would do anything to have that kind of control over their picking (expect practice it for hours and hours :D).
On your trills, if you haven't tried this yet, try it with a metronome. Start slow, at 40 or 60 bpm and do one note per beat. Hammer-on, pull-off, hammer-on, etc. At such a slow speed you get a much clearer recognition of the dynamics of every note and you'll learn how to put on more or less force to make all the notes sound equally dynamic.
Regarding keeping your "turkey butt" under control, again, just focus on that aspect of the control (without the left hand) at increasingly fast speeds. I have gotten very good at keeping my fingers in but I still have to concentrate on it. Whenever they start sticking out it's normally because I'm picking beyond my skill level and I'm tensing up to compensate.
I have the same sort of problem with the fourth finger anchor when finger picking, and I've had to slow down some songs I've been picking for 20 years so I can concentrate on picking them with my hand floating.
Basically, the sum of what I'm saying is that what works for me is slowing down whenever my form gets out of whack. It means I'm tweaking myself so I can try and play uber-fast, and my form goes downhill and I sound terrible.