Perhaps I just didn't hit the right combination to get it to work though it wasn't from lack of trying!  Hopefully, you will figure it out.

Have you tried modding the population loot function? It may let you get any resource in loot for each unit killed. 

Regarding bows, any spell marked as israngedattack essentially performs a ranged melee roll. It is different from a normal spell cast and a normal melee attack. That's why you're not getting your modifiers to work.

I have sent a PM to Derek Paxton in the past explaining why we need a way to properly do "spells" from groups where each attacker does his own spell including hits and misses. This isn't just about bows, it's also about having groups with special abilities which is currently more or less offlimits. Think of how poorly the THrowing Knives work for groups for example. Hopefully Derek Paxton will pick up on it.

I seem to recall A_Looting as a percentage of increased gildar after battles. But that was back in E:wom when gildar actually dropped from battles.