Well ... I can't be of much help. Using a flash seems like your only option to stop motion if you don't want to use fast film. But others here may know another way. For what it's worth, here are some under what I imagine to be similar lighting, which I took last summer using Tmax 3200. These are scanned from the negatives, not prints ... so it's hard for me to know what's grain and what's noise.
Also, the lens I took these with wasn't the greatest.
I definitely want to avoid a flash, but am certainly not entertaining any thoughts of using a slow speed film - not now! I might be able to get into rehearsals, in which case I might me able to do that then.