Hi, I had the same mainsystem.exe crash problem after fully installing the game and applying the english patch ("SCEFPatch.exe" in the "SCEF_Patch74.rar" file), and your post was really helpful!
At first it was still crashing even after checking the "Disable display scaling on high DPI settings"; after some trial-and-error, I finally got it working by checking the "Disable desktop composition" box by itself.
N.B.: Windows 7 user with a 64bit processor here.