I did two kvas so far. I started them with the assumption that kvas was a farm drink used in the old days to salvage old and stale bread. So it was not designed to be fancy but rather to make a refreshing summer drink with cheap ingredients. for this reason I didn't use pumpernickel but stale...
I have the same problem with my false bottom and I'd like to put a gauge on my pump inlet just like you did. Do you have a catalog reference for the gauge?