I know that Shadows can NOT be on Ultra or it won't work. Set them to Medium, exit out of the launcher, and then edit the file. Do not go back into the launcher after saving the settings or it might jack them up again.
thats what I did, didnt work, whenever iShadowMapResolution is set to 4096, the game just set the shadow to ultra even if I don't go through the launcher. I even set the file to read only so it won't get override. The screen shot N_B post show shadows at much higher res and than the one in your screen, like perfectly straight edge. I also tested his method and it worked, but the draw distance is horrible.