First Problem: GTA 5 has terrible performance when using DXVK. I get less than half of my original fps
DXVK has never performed well on ancient hardware, especially not on ancient hardware that doesn't even get driver updates anymore. Kepler is entirely expected to lose 30-50% in GPU-bound scenarios, and GTA 5 is also one of those games where CPU overhead with DXVK is not great compared to native drivers, so running a 12-year old CPU also doesn't help.
If it doesn't work for you, don't use it.
The game crashes when I try to access the "Graphics" tab in the settings
Literally works fine here.
Some dick on Discord
This "dick" is one of our main contributors, and our stance on Windows is fairly clear.
Nothing extracted yet.
Software information
Grand Theft Auto 5
System information
First Problem: GTA 5 has terrible performance when using DXVK. I get less than half of my original fps
Second Problem: The game crashes when I try to access the "Graphics" tab in the settings
Also, my card doesn't support Vulkan 1.3, thus I use DXVK 1.10.3
Some dick on Discord said that you don't support Windows. But as far as I'm aware your files are available and work pretty well on Windows, so you might aswell support it.