What % protein is your all flock? Where I am, we have kent (blue seal) and their all flock comes in, I believe 22 & 28%, which works really well for the different ages.
The brewers yeast from ( at least my) the elevator is pretty low in protein. I believe its because it isn't separated out from the culture before being dried to feed. I feed it because of the nutrients it provides, just don't depend on it to increase protein %'s.
As a small part of his diet it wouldn't be too bad, but the increased Ca and other nutrients designed for egg layers are NOT good for any male bird and could eventually lead to liver or kidney problems. I believe you would be better off continuing to feed the all flock with freely available...