Welcome onboard.
Perplexing problem which sounds like loose, possibly arcing connection around fuse panel. I would discount bad bulb since there are many involved. A few questions:
Is fuse 31 7.5 amp the one you checked and confirmed as OK?
Are pw and pl switch lights on doors working?
Rear license plate lights?
Intermittent wiper speed and w/s washer functions OK?
You have replaced headlight switch? There was recall on switch/connections thereto, latter causing heat build up. Don't know if your year of car involved or not, my '97 was recalled.
Any recent work in dash area, e.g. radio?
I can't relate to your description of wires/connectors at fuse panel and Winter temp precludes me looking at my own for comparison. However, answer above and I'll keep an eye for your post and see if we can work this thru' since I have '97 wiring manual as a reference.
