#1: Object damage are simply damage done to structures. It doesn't matter what kind of building, a 20mm round for instance will do the same (object) damage against a hangar as against a 40mm AA gun.
Your 'Object Destroyed' Score ARE affected by what kind of structure you take out. A hangar will be more than an ack for instance, but I don't know the exact points for each object.
#2: Yes much like #1. It doens't matter what kind of plane, it only matters what kind of round you hit it with.
#3: Your 'Kill score' works kinda like the 'object destroyed' score do for Air to Ground. From what I have seen a kill or assist on a plane will give you between 1/8 and 1 in kill score. I don't know if it depends on its type or how much damage you inflicted on him before he died tho
Your total fighter score will be the sum of the 'plane damage' and 'kill score', with the plane damage being the far biggest contributor.
Snefens
Aces High Training Corps