[i]"1) Sloppy pitch fishing! Somehow, time after time, when I tried to sneak a listen to find my opening pitch, I couldn’t hear anything… so I would lift my left hand a teensy bit higher… still nothing… a little higher, still nothing… and then it would be time for me to enter, and I had to bring up the volume to a level clearly audible to the audience, and correct as quickly as I could. In some cases, my hand was a third or more away from the desired pitch. Yuk."[/i]
You may want to consider placing your theremin monitor at ear level within arm's length of your right ear. Indeed, at that distance, every little "flaw" in your playing is obvious to you. However, you can correct the pitch before the audience notices the correction.
You may wish to consider use of a pitch-preview. A pitch preview would help you with entrances after long rests.
[i]2) Shaky starts, probably a direct consequence of the above. The first phrase of each selection tended to be messy, especially with regard to intonation. The longer each item went on, the better I fared.[/i]
Pitch preview. Give it a try... :)
[i]3) Mushy attacks. Mainly a symptom of pitch perfectionism, trying to get each pitch just right before bringing the volume up to a level audible to the audience. In real life, there just isn’t time; I need to practice a more confident left-hand technique, in conjunction with drilling my right hand to find pitches more reliably, instantaneously.[/i]
Try practicing without using your left hand. Just put your left hand at your side and play the melodies. This is counter-intuitive, I know -- however you are trying to do too much with your left hand. Particularly for classical music -- let your right hand deal with details and let your left deal with the "big picture" of long, arched, crescendi and dimenuendi. Strive to get "waves of sound" rather than individual notes. You can do it!
Don't "drill" your right hand. "Drill, baby, Drill" doesn't work that well for theremin playing :) . It is all about hand/ear coordination. Don't try to "hit" notes... instead, learn how to move to them securely while listening. Practice slowly -- exaggerate the glisses if you need to at first -- once you develop hand/ear coordination the speed will come.
Try to "reach" for notes rather than to "hit" them. That is, an undershoot corrected to pitch is preferable to an overshoot that is corrected back in the opposite direction. Check out the Clara Rockmore recordings. Her approach to glisses melds both style and practicality.
On sustained notes, never stop "working the notes" -- keep trimming them to pitch. Remember that you, as the performer, will tend to hear the top of the vibrato cycle -- place the top of your vibrato slightly above your target pitch. This takes some getting used to. The wider the vibrato, the farther the top of the vibrato sits above the target pitch.
I hope you don't mind these comments. Since you posted a self-critique I wanted to offer some ideas that you might want to explore.
All the best!
[i]-- Kevin[/i]