Here's an update on my tire situation.
This morning, the tire was flat. I blew it up to about 30 psi, and went about doing some other work while the tractor sat. When I was finally ready to use the tractor, at about 1 PM, the tire was flat again. I blew it up to 30 again, and used the tractor through the rest of the afternoon. When I put the tractor away, at about 5:45 PM, there was 24 psi left. I checked again, at about 8:15 PM and there was 21 psi left. It is still leaking, but at a slower rate.
Yesterday, after reseating the tire, I only carried two buckets of gravel a short distance, then put the tractor away. This afternoon, I didn't use the tractor hard, and didn't carry any gravel. I am in the process of moving my 8' x 16' shed, and there's jacking and blocking, etc. to do. I moved my skids with the tractor, and tugged the building part of the way. Darkness set in, so I will have to finish in another session (or two).
My theory (and hope) is that, with use, the beads will seat and seal better. If not, I may have to put a tube in it.
I have another thought, and wonder if any of you have tried something similar. What if I dismounted the tire again (taking it off the tractor this time), cleaned up the tire beads and the rim well, then used silicone caulking as a lubricant and sealer for reseating the beads once more. That stuff is quite slippery when wet, and should help the seal when it cures.
Before moving, I gave away a tire changer, and my old shop compressor to my son's father in law. He said I could come use them any time. I will likely take him up on that if I wrestle with this tire again. It's a bit of a trip, but worth it. Besides, the guy was a friend of mine long before my son married his daughter. It would be a good excuse to visit with him.