Darn, that's exactly how my video settings are setup. If my specs are so far beyond yours, I wonder what the issue could be...
And here is what I'm talking about. First, stock game, no mods whatsoever, maxed graphics settings, German mission 3 (50-55 FPS):
Kursk Mission 1, installation in a different folder with ONLY ZeeWolf mod (I have multiple TvT installs to run different configs - MAYBE this is a clue...) (8-12 FPS):
...and just for fun, with ALL graphics settings set to minimum, still hardly a good frame rate(15-20 FPS):
Again, I commend you for your excellent work - I just want to enjoy it @ 55 FPS some day.