Okay, a brief update on the electrical problem. Despite temperatures that were only barely above the teens today, I removed the driver's side door panel and examined and tested the headlight switch, and it seems to be working properly. So, good news - although conducting all this disassembly and testing would have been more fun in April or May.
The next stop on the diagnostic trail would seem to be the fuse box and apparently the relay that's also under the dashboard, which transfers power to the instrument panel and the tail lights, when the headlights are turned on.
A couple of things I don't understand. The first is why the "warning chime" is sounding, even when the headlights are turned off - which is the same chime you would hear to remind you if you left the headlights on (accidentally) and opened the driver's side door. Even though the headlights are clearly turned off, this seems to suggest that something in the circuit (tail light / instrument panel) is still energized, even though the lights are not illuminating. I'm sure that's somehow significant, although I'm not sure how - or why.
Likewise, I can't figure why the fuse box doesn't list either the headlights, tail lights or instrument panel, although the instrument panel (IP) seems to be listed under Fuse #21 (which I've checked as being OK). Well, I've included a thumbnail to the fuse box listing, and I'm open to additional suggestions. Thanks.