I did find the display driver for the w580i online and tried to replace it with FSX through XS++. The replacement worked, but that didn't fix the problem. I guess the problem is, that on the W580i, you cannot switch firmware versions. I didn't know which version I had originally, but I tried them all and R8BE001_RED52 was the one that worked for me.

I used Setool btw, xs++ was giving me trouble with swaping the custom pack files into it's directory folder.