Nicely done, the effect of storm is created. I usually do that with good red filter and Tmax 100, (Tmx has higher sensitivity to red than average film.) Too bad, that DoF was too shallow for the sky. At least for me.
Maybe controlling DoF in camera would be better method then trying to fix it in PP. With such a landscape shots is something you should do, I always go for the smallest possible and practical (for given lens) aperture with landscape.
I did adjust DOF in camera. I normally shoot at f16-22 for most landscapes. This one was a quick jump out of the car with whatever was last setting with camera. I have more shots just none where that cloud was in position.