Well - I just got back from an extended trip overseas and FINALLY got around to working on this. Definitely did the trick - have refilled the water tank and fired up the pressure pump to see if we have leaks... All gone!
The kicker - the dealer rep, while doing the walk through, told us "yes, the small drip from there is expected at the low point drain, that's what its for - condensate from the A/C goes out there, and any sloshing of the tank when it gets filled or when the trailer moves -it all comes out there by design."
WHAT A FREAKING LIAR!
Anyway - the problem is solved now. (And I have STILL yet to hear back from the dealer to arrange a time to bring the trailer in for troubleshooting. Man did I get a DUD dealer!)
Anyway, thanks for all the helpful suggestions. I had to remove a panel in the pass-through storage to get at the 3 valves, but they were exactly as described and cycling them open and closed several times seems to have sealed them. Hopefully permanently!