PROBLEM SOLVED!
After 8 hours of labor today, all is now well with my right rear wheel.
I was able to remove the wheel and drum by using a "hub knocker" that a friend lent me. You screw it onto the axle, then whack it 3-4 times with a sledge hammer, and presto! Off comes the drum (still attached to the wheel).
Then the real fun begins. I tried nearly every suggestion (except the freon idea) offered, but that lug and nut were determined to hold together and spin together. I finally decided to destroy the lug nut with the hope that thereafter I could press the lug itself out the "backside."
Had to grind away on the nut to remove all its shoulders, so it could pass through the hole. Using my air-powered grinder, it was a chore to get at the nut while avoiding cutting on the spokes or wheel hub.
I finally got most of it removed (see attached photo), then drilled successively larger diameter holes from front to back until the whole thing came apart.
Pressed in a new lug, installed a new tube in the tire, and put everything back together.
I've been playing with Model A's for nearly 20 years and have probably installed and removed lug nuts a few hundred times. Never before did I encounter a lug and nut bonding like this.
The lesson I learned is that I will never, ever, EVER again install a lug nut without applying anti-seize lube to the lug threads.
Thanks to all for your sharing your ideas and experiences.