Problem solved! I started from scratch, raised the VTA a smidge, re-cleaned the stylus, and reset all of the connections. Whatever was wrong is now right. It is as if two thick blankets have been removed from the speakers and the cartridge is now singing beautifully. I've got a little hum issue I still need to work on, but at least now I know the cartridge is not defective. Far from it!
My sincere thanks to all who weighed in with constructive comments.