Just wanted to post to (hopefully) close this out. The 3rd brake light is still working since the fuse replacement a few days ago. I'll point out that the #2 fuse was removed and re-installed several times (always visually inspected not blown), and there was no obvious sign of corrosion on the blades of the fuse, nor any obvious indication there was a faulty connection at the fuse terminal. Checking continuity of the fuse with the fuse in place- showed the fuse was good. I was going to jumper the fuse with a fused 12 volts as doc suggested, after I checked continuity with the multimeter one last time. I was holding one probe on the fuse firmly, and when I dropped the other probe it grounded on my jack (under the car for another issue) which blew the fuse. I replaced the fuse- and the auxillary tail light is now working.

I honestly haven't had this happen before on any of our cars, (fuse not making connection in it's holder) and can only assume it has something to do with the quality of various electrical components we all know were used in the 90s and forward. I suspect the only "fix" would be a preventative meausure, and would be to remove each fuse, hit it with sand paper- slather it in dielectric grease and replace. Thanks to MBdoc for the help! -J