I found the answer on consimworld:
3.)The MACV platoon is in Zone C. It attacks into the Jeanne d'Arc High School as the assault platoon. May it advance into the high school after the first round? The rules say the MACV platoon can only move into zones adjacent to the MACV complex, and the High School is not ... but technically this is combat, not movement. So, what's your judgement?
The MACV Platoon can notattack the Jeanne d'Arc High School alone. Because, when you attack, you have to assault the zone (trying to enter the attacked zone). Ok ? But the MACV platoon can still support this attack if another platoon is assaulting this zone.
So yes, the MACV can support two hexes away but can't enter the hex.
The Civilian event would prevent an end fight even with both normal units I think.
Edit: the civilian event is also clarified on consimworld:
The answer is : the ombat is not mandatory over, you can begin with a 1st round if you wish. If the NVA unit is eliminated in the roll triggering the event, treat it as "no event".
I will add this to the errata.