UPDATE: I couldn't remove rear wheel so I took it to the shop. This is what they said:
"drained rear drive oil-no appreciable amount of metal on
magnetic drain plug, but significantly overfilled. tightened
axle and confirmed that wheel does become difficult to
rotate when torqued, attempted to remove axle, found
that wheel bearing inner race was siezed to the axle,
was able to remove it by removing the mufflers and
forcing it off of the axle. found that the inner wheel
spacer adjusting shim was missing and wheel bearing's
cage is broken. needs bearings, seals spacers and
shimming. also needs rear tire-tread depth is 0."
I can't believe the inner shim was missing! Happy to be alive.