Success at last (at least in getting the tire off of the rim) ????
If nothing else, I don’t give up easily. Perseverance paid off.
This morning, I took my front wheel to the window glass and screen shop where I work. There I have access to a round, hard plastic trash can, one of a few “tools” I used to finally unseat the Nobby Nic from the rim. At first, I leaned over the rim with my nearly 200 pounds and pushed hard with gloved hands. Nothing. While rolling the tire trying to expose the bead, I tried to work a tire lever between the bead and the seat – not even close. Using a thin, stiff, blunt plastic tool used for shimming glass, I was able to at least slide past the bead and touch the base of the rim. But I still could not get a tire lever to be of any use. Reluctantly, I wedged a small flat blade screwdriver between the bead and the base, trying as best I could not to scratch the seat. After several attempts, finally the bead broke loose. One side of the tire was free, but the opposite bead was still seated very tightly. The stiff glass shim broke the other bead loose, and I removed the tire.
I was surprised by the amount of effort that this required, and it makes me anxious if ever I need to insert a tube while on a ride. Unfortunately, some damage was done to the tire at the bead face, but fortunately no puncture. Despite the minor damage, I plan to mount this tire to complete my tubeless conversion. Soon enough, I will learn whether this tire will work or if it needs replacing.