I have limited experience with GPu pass through, but from what I've learned when I tried to do it with limited success (because of hardware limitations):

1. That reddish post is two years old, it's ages ago regarding VFIO or GPU pass throug, look for for modern tutorials, preferably for the same hardware (GPU) or distro;
2. There's no single way or "standard" of doing things, but if you mix parts of tutorials it may not work in the end, try to understand what's done and apply to your setup;
3. Regarding hooks, test them with simple commands with some output first, so you can verify they are working as it should first, and try the VFIO related commands manually too so you are sure they do what you want;
4. From what I've seen, if the hardware supports VFIO/pass through then it will work usually after a few tries, if it doesn't then there's a big change you have some hardware limitation, many times related to a bad or broken BIOS/firmware.

Good luck!