Thanks for the feedback and the ideas!
The gun balancing is definitely not finished. For the Kar 98k I could just drop it's price and buff it's damage a bit so it could be more useful.
I have indeed consider some dynamic map events when I was talking about a church level, for example: every few rounds fog becomes thicker and you have to go inside the church and barricade it and try to holdout in this relatively small building. But at this point I am pretty sure I will be going with the Nuclear Plant idea so I'll have to think of some other interesting dynamic-ish event to add.
Some sort of slow-mo powerup is also a possible addition.
"Werwolf" idea sounds interesting but people might get confused as to where are the werewolves :D. With that in mind I could just create some fictional name for this group and make the story based on that.
Anyway, I really appreciate that you took your time to give detail feedback and some interesting ideas.