UPDATE:
Brakes lights are working again!
This evening, I removed and replaced all the bulbs, checked the voltage on the third brake light, and sprayed electrical contact cleaner inside each light socket as best I could. I also cleaned and sprayed the 6 pin connectors at each side. Finally, I went underneath and scraped away the road gunk from the wires and around the back of the fixture. (not sure what that accomplished, but it made me feel better. Also, rechecked the all grounds that I could reach easily, and gently checked the wires/connections in the engine area.
Originally, I tried to remove the entire fixtures not inspect the connections and grounds in the back, but i stripped one bolt, and spun another that never backed out. I'll leave this job for an entire weekend when i can devote the proper time for complete fixture removal, electrical cleaning, ground checks, etc.
For now, everything works...
Thanks to all for the advice and suggestions!