Upward pick escape motion

The video attached is me trying to play upward escape motion at 120bpm. I can tell I'm not getting it, but I don't know what to practice to improve. I can do tremolo picking by moving my elbow but I can't change strings when I do that. Also, I don't want to work on that. My goal is to be able to play wrist motion tremolo at 150 or 160bpm. It's gotta be possible, right? I'm not even close. What do I practice to get there?