1. When a vehicle moves, do we add an Exposed marker to it?
No, if vehicle that is activated and moves in the vehicle phase, with the flip side of the activated marker to show it moved, since AT combat is conducted as it happens in the vehicle phase, it is not typically necessary to mark a moving vehicle. The AT combat table has a moving target modifier (+1). Unlike exposed, a moving AT target is harder to hit than a stationary AT target
2. There doesn't seem to be an Exposed modifier on the AT Combat resolution table, does this modifier exist?
3. Also, again on vehicles: when a vehicle performs a normal attack during the Combat Effects phase (say against infantry), is this handled under the normal (all unit) fire tables and modifiers, or the AT Combat resolution table?
Many vehicles exert a VOF, those with a printed VOF exert it just like any infantry unit against infantry targets in the Combat phase
For example, a US M4 Sherman exerts a H VOF. If it moved into a card and become the target of AT combat from a German squad with a panzerfaust the Net AT Combat Modifier = Defensive Factor (+0)+ Moving Target (+1) + Panzerfaust Attack Factor (-3) = -2. If you draw a high number and the Sherman is still in action, in the ensuing Combat phase the German squad (assuming it was already spotted) must face the Heavy Weapons VOF (-3)...
Thanks in advance
You are welcome