Just a couple of clarifications needed:
Can a lone PAVN "dummy" hidden move marker trigger an ambush? No actual assault would be performed, but the FWA stack's movement is now over, and the hidden move marker is revealed and places 2 turns ahead.
No, first sentence of 16.6 "PAVN Hidden Movement marker concealing units"
FWA Ambush (18.5 optional rule)
I'm assuming the +1DMR is applied to the PAVN during the upcoming maneuver combat (assuming maneuver combat was declared), while the -1DMR is applied to the defensive assault roll of the FWA unit (assuming assault combat was declared)?
Hmm, those are not clear. Correct, the PAVN should get a +1 DRM on any Maneuver Combat, and the FWA should get a -1 in the Assault.
How are you liking the game so far?