Instant crash when trying to play this game Full Screen in any resolution.

Will only play in Window. i7 5820k, X99, GTX 980.

Have you tried going under advanced settings and changing the "Max Voxel Threads"?

I found that I did not notice any real performance improvements on my core i5 3570k going to this latest patch and I suspect that the improvements are mostly for hyperthreading users (which the core i5 3570k does not use).

However I noticed that the Max Voxel threads that you can choose is 8, whereas you require 12 to utilize each of your cores correctly, perhaps this might be the source of the crash as it cannot allocate the 8 threads correctly to the 12 virtual cores (6 real).

Try choosing 8 threads manually within the "Max Voxel Threads" option under the "Advanced" tab, if that still causes the crashes, try different values until hopefully it works.

*EDIT*
Sorry I just realized I did not read your post very well and that it is working fine in windowed mode, so I don't think this will be of any help (well if it worked fine before the patch and now it does not, perhaps it still might work)