datafox...have you ever heard of the little riddle of the patient who goes into the doctor and says: "Doc, it hurts when I do this?" The doctor looks at the patient and simply says "Then don't do that!".
By your description it sounds like you are keeping your arm on the arm rest to the point of severe pain. My question to you is why didn't you move your arm the minute it started hurting..instead of seeing how long you could go and then have repercussions from it with twitches?
Since you are getting an EMG on Monday, I would try and relax till then as your dr.s have also said to do. Sounds like it is going to come back clean and you will be just fine...according to your neuro. Also, if the dr. says you have no weakness then that means that clinically you do not. You may feel fatigue in your wrist, but you should not write weakness unless has been clincially defined as so by your doctor. To me it sounds more like a pinched nerve or early onset of carpal tunnel causing your symptoms. Good luck to you and try not to worry, by the symptoms you have described you do not have ALS.