the pc mouse is too sensitive, even on lowest sens settings. is there a chance to set a lower speed to the mouse?

Your problem might have something to do with this: http://pcgamingwiki.com/wiki/Armed_and_Dangerous#Gameplay.2FPhysics_Speed_problems_on_modern_Operating_Systems

Try disabling mouse acceleration (Enhance Mouse Precision on Windows, in mouse pointer settings), or disabling your mouse driver if you have one. It might help, acceleration disabled helps a little bit on my system. Still, the best way for me is to directly lower the mouse DPI setting, if you can (you probably have a setting for this if you've got a gaming mouse, if not I think I've read about a soft for that some time ago).

Also try polling rates, also found somewhere in gaming mouse drivers. It has proven useful for some old games like Dark Reign 2.

Have you tried using NVidia Inspector (or the ATI equivalent) to cap the game at 60fps? This worked for me.