The problem has been solved! Thanks again to everyone who replied and once again, to this forum in general.
I replaced my ailing stock 70A alternator with a new Bosch 80A (66X) alternator. All symptoms are gone now. Cars runs perfectly.
I did some before and after battery multimeter readings right before I did the swap -
rest - 12.85V
idle - 13.86V
idle with full load = 11.87V
full load, 1500 RPM = 11.74V
rest = 12.88V
idle = 13.97V
idle with full load = 13.56V
full load, 1500 RPM = 13.94V
A few other unexpected pleasant surprises awaited me as well - I had an annoying flicker of my instrument panel lights at idle - totally gone. Lights are all nice and bright. The monowiper now zips across the windshield crisply and the washer jets spray properly.
The reason I decided to finally abandon the old alternator and install the new 80A alternator was made for me by Santa, er, my wife. She bought me a new Alpine 4-channel V-power amplifier for Christmas to further upgrade my stereo.
It was easy to install the new alternator. 2.5 hours total. Old one came off easily and I took it off without removing the serpentine belt. I loosened (but not removed) the fan shroud and I just loosened the two mounting bolts (13mm) and the old alternator slipped out. I cut the old wiring harness near the base and there were three wires - two 10 gauge wires and one smaller (16 gauge?) wire. I soldered new eyelet connectors to each wire and sealed with heatshrink. The 80A (Bosch 66X)alternator doesn't have a plug in harness, it has a large bolt and a small bolt to attach the wiring (see picture here in the Fastlane catalog). The two large wires go to the large bolt and the small wire to the small bolt. That's it - thanks to M.B. DOC for that info in another post!
To install the new alternator, I slipped it roughly into place and got the belt on the pulley first. I then attached the upper mounting bolt. Then, from underneath the car, I pulled down hard to get the alternator into place for the lower mounting bolt. It took some strength, but I'm no Hercules (no pun intended) and it wasn't that hard. I had the lower bolt ready in place, so once I had leveraged the alternator into position, I slipped the bolt home and tightened it. That's it, no removal of the belt necessary - not sure if everyone is this lucky, I'd hate to mess around with the tensioner. Belt tension is fine (and the serpentine belt is in good condition in my car, btw).
So that's it, I've got a new alternator, a happy Benz and a great new project to look forward to - installing my new Alpine amp. That's a post for another section though. Life is good!
Thanks again to all!