Sounds like you've tried pretty much everything I'd recommend (including reinstalling dependancies from the Steam folder)...
The only thing I can think of is that you should uninstall all PhysX (and possibly other NVidia drivers) from the windows control panel - then try reinstalling the latest versions from the NVidia website.
My guess is something was corrupted in your last NVidia install. I'm running a complex NVidia system (3 cards, 2*SLI + an older third card for PhysX) and i've never had issues with DKS. You might try reinstalling other files in the support folder (the Visual C++ redistibutables have caused some issues in the past).
Anyway, best of luck, and welcome to the forums! I'm sure someone else can offer more help than I have.