It finally works!

It's taken years but the game finally works! You just have to use Glorious Eggroll's Proton, version 7-13 in my case.

I haven't had the chance to put some real time into it yet, but the only problem so far is resource overlays aren't working. I'm not happy about that, but the game is working now and that is a huge step forward!

Other notes:
You can force multithreading, and vastly increase performance, by setting this as the launch option:
taskset -c 1-$(($(nproc --all)-1)) %command%

You can also put a frame cap on the game with:
DXVK_FRAME_RATE=60

So the full launch option would be:
DXVK_FRAME_RATE=60 taskset -c 1-$(($(nproc --all)-1)) %command%