When I install, my FH crashes. How can I fix this?
You don't install it. Just extract the archive and launch the FeralHeart.exe inside of it. Do NOT drag and drop everything into your normal FH folder.
I'm having the same issue, I don't have any other version of FeralHeart installed either. I extracted the folder using 7zip and launched FeralHeart.exe, it crashes right away.
Edit: I downloaded the normal FeralHeart client, ran that, then ran FHD and it worked. Not sure what happened there.