First TC

I've been playing guitar for almost 30 years (I'm 38) and feel like my technical ability has a bit of a handbrake on it. I can tremolo pick around 16th notes at 200bpm but can't keep it up for long as a lot of tension builds up in my forearm. My natural inclination seems to be a wrist-motion, downward pickslanting/upstroke escape motion with my palm resting on the bridge (as demonstrated in the first part of this video). I feel I can get faster speeds when I let my hand hover about the strings but my precision and ability to change strings suffers from this. I also seem to be able to pick downstroke 8th notes at 210bpm and sustain it longer than 16ths at 200bpm. I can fairly easily tap a guitar pick against a surface using what I believe is the same motion at around 220bpm. I also seem to have an issue with hitting strings when trying to string changes at fast speeds despite an apparently escape motion in my playing. I feel like perhaps there is an inefficient motion that I am using to reposition my hand from one string to another that is interfering with my overall technique. I've included a quick run through examples of all of the above in the video. I am just looking for some experienced critique of how I'm playing and what might be getting in the way of more comfort and fluidity at higher tempos. Thanks!