Malin:
My answers to your questions, in the order you asked them, are:

Yes--some of the time

The words were not Nolan's

Your guess is as good as mine

For a recent summary of the Nolan incident see: pages 253-54 of, The Black Regulars, l866-l898, by William A. Dobak and Thomas D. Phillips (University of Oklahoma Press, 200l).

For the most recent book-length study refer to my message on 9/5 re Paul H. Carlson's, The Buffalo Soldier Tragedy of l877