1 The mod only looks at the "enemy" faction and then determines what to drop, and how much, based on whether its a "unit" (biters, spitters, any other units other mods may add), a "turret" (worms), or a "unit-spawner" (nests). If a mod adds biters into another faction, which is what I'm assuming the biters faction mod does, then those are currently not taken into account.
I'll take a quick look at that mod, shouldn't be too difficult to implement.
2 I haven't played with Krastorio/Warmonger yet, but I'll add it as a request. One possibility could be to also drop xenomass when mining the creep, another would be to ignore xenomass entirely and substitute is for biomass instead.
One thing I do want to mention is that apparently the original mod had a feature that automatically marked each drop for deconstruction, so bots would try to pick them up immediately. Don't know why that was removed entirely, but that could help with lots of drops piling up.