Well, that seems to have been a cheap fix- I reinstalled the drive and rode it for about 15 minutes yesterday, which was a good thing, considering I still have breathing problems from COVID. I still feel the tire tread, and did seem to feel it more or less, depending on how hard I pedaled and which gear I was using, but it never rumbled or became more difficult to crank.
Thanks to all for the comments.
Bottom line for anyone who feels the need to change the oil- pay attention to the viscosity.