Armor Piercing, Flaming Arrows, and Fire Damage

[tinkthank]

Maybe some smart folk here know:

When I cast Flaming Arrows, it gives my ranged units the appropriate Icon, which when clicked says "8 AP damage" (I think).

- I am betting this is 8 AP damage over and above the damage a normal bow/javelin/hot dog would do. Right? Is this treated in a separate roll, or does it *add* 8 points of damage to the normal arrow damage and make the whole basket armor piercing?

- Nowhere does it say "fire damage". Does anyone know if fire resistant troops (e.g. abyssians) are resistant/immune to this damage?

- With units with a fiery ranged attack, such as Demons of Celestial Fire, I can cast this spell and see they get the little icon too. What is the deal here, since they already have AP damage, which also is probably fiery (?) -- do they just get +8 damage?

thanks in advance