I like it.
And to your problem no.1:
Well, I dont think anybody will call you something like that just because you show these stuff... As long as you dont show it in a positive context. If you make clear "this is the enemy, and he is evil", I dont see why people should complain...
The only reason why Hookcrosses and other Nazi signs are removed from the German Wolfenstein versions is that they are kinda illegal, and as your a german developer, THIS could become a problem... Even if you dont sell it...