I HAVE THE SOLUTION!!!! PLEASE READ
I haven't updated my mac, and I'm not sure if this will work, but it was my holy grail when my mac was totally rejecting FH awhile back. It's not hard to do, so try giving it a shot. 'tis very simple.
1. delete your current feral heart folder and game files. you can save certain folders you need like exports and presets, but delete most of it.
2. download the WINDOWS download instead (trust me) and once it's done, open up the folder and find feral heart.exe. right click and select open with>wine.
NOTE: if wine is not displayed as an option even when you click "all applications", download the mac download files instead simply for the wine gecko and mono packages. Then delete the folder and try opening the .exe with wine again.