I checked the output of the video from this week, I still set it darker than it should have been. I used the dance club preset, having used the concert lo-lit preset the week before. I had tried either rehearsal studio or garage preset a few days earlier at another venue, only for them to turn extra stage lights on as soon as I was behind the keyboard on stage. I will need a bit more trial and error to settle on presets to match stage brightness, I may check a video editor as it should be close enough to adjust the level afterwards.

I taped a card above the Zoom, and that fixed the shine effect on the lens. And I used a powerbank instead of AA batteries, no issues with either.
I brightened up and cropped some pictures from the guest act, just to focus more on the sound from placing the Zoom just in front of the stage.