The consultation with the doctor revealed the following observations or recommendations:

The calluses surrounding the blood vessels were, indeed, created by the body to protect the vessels due to the repeated pressure put upon them in the forming of barre chords.
Surgical intervention does not appear to be necessary.
Two remaining options seem to be either to rethink the positioning of the finger or to avoid the barre chords altogether.

In other words, the doctor had little to add to what has already been said here. She was greatly apologetic in that she didn’t know enough about guitar playing to advise me more about possible solutions with regard to technique. However, she felt quite sure that the options she outlined were sound. (So did I.) She also offered a prescription for an anti-inflamatory drug that may help to speed my recovery.

Recently I discovered that I could actually play barre chords on my wife’s nylon stringed classical guitar without discomfort. This was a joyous breakthrough! Nonetheless, I have continued to avoid such chords wherever possible. Also, the calluses have by now dissolved almost completely, allowing me to be able to play my twelve-string once more - at least a little. The twelve-string (Martin D12-28) has a much lighter action (by far!) than my old Yamaha FG 160 six-string, aka, The Mudcat Adventure Guitar. Although it developed a very fine sound after I refinished it, the Yamaha’s action has always been its most evident flaw, making it the obvious culprit with regard to my damaged finger. And so, I’m afraid The Mudcat Adventure Guitar may have to gather a little dust for a while. I’ll miss it terribly.