Re 6: My point in 6 was badly stated. What I meant was: at the prior performances, I kept the D7000 at ISO 6400 because the stage lighting was so dim, and saw horrible noise when doing "extreme" crops. That was the genesis of this thread.
At the recent performances, i kept resetting the ISO manually down as low as "possible" above the LO warning (to reduce noise. Both sessions were speed priority (1/200). Most of the shots in the recent session don't look underexposed, they look over exposed. OR, I confuse over exposure with over-saturation (which seems definitely to be the case, especially for reds, whether or not there was also overexposure. (I need to pick some samples to post. But I need to sort through a huge file, which I have been going through.)
Re: Using the SB 600. I can try that. Would you care to suggest a type of diffuser? I just use StoFen, as it is neat & unobtrusive. There are hundreds of diffusers. Have you seen the Rogue Flashbender: it's a flexible reflector that straps on.
About the P&S flashes. They ARE very obtrusive. They are very distracting. They bother me, too, when I am shooting flashless (always). I did not know that the 600 would be unobtrusive. How far from the camera to set it?
Re my point 5b. Your reference to remote flash in your prior post,which i quoted, had a sort of odd grammar, so i did not quite understand. Please refer back.
re D3s. I don't have friend who has one, but the one local camera store that has (sort of) survived the recession & the on-line competition -- they had to merge with Calumet and shut all but three of their local stores -- is Penn camera. They sell & rent equipment. Renting the D3s costs $180 (you heard me) for one weekend.
I see that you suspect that my pictures were not in focus. Is it possible that there I am seeing (perhaps also) flare from oversaturation?