OK, so for anyone who's interested, it seems like the WD40 soaking made a diff, with some encouragement this morning, the rear axle came out, and the new tire is on. So now I have a couple more questions: (1) why did the rear axle corrode so bad (I wire brushed it and coated lightly with anti-sieze before reassembling), and (2) what are the dimensions / threads of the rear axle pinch bolt, since mine went missing at some point. Thanks in advance!