I've been through 6 months of facial myalgia due to grinding in my sleep and my dentist gave me an exercise which helped a bit and in the end mine went on its own. Clenching & grinding seem to be a cause. I didn't go the nightguard route though as I had read that they can be different to sleep with and I really didn't want to interupt my sleep at that bad time.
The exercise, in case its any use, is in this thread which also includes a link to a previous edition to a book I have on trigger points which may be of use as it covers TMJ:
http://www.nomorepanic.co.uk/showthread.php?t=166483
In terms of twitching, I found it was always more common & intense when I was at the worst stagees of my anxiety. As I started to recovery, it went away on its own but I still get them from time to time but they are nothing now and don't bother me. I can remember the strong ones that make your arms & legs suddenly shoot out...it was like I wasn't in control of my own limbs at times!