Unfortunately, those settings are hard saved to steam saving system. If you are still having issues. Follow this guide on how to erase your game data to have a fresh start.
https://www.youtube.com/watch?v=UP01HAfd4ro
Be warned, it will delete your save files but will mean you will have key binding support:)
UPDATED: FROM USER ADLEY
i found the saves folder. its in C:>users>(yourusername)>appdata>local>Fifteendays>saved.
the save game folder itself is named fifteendays somehow not 9 days. i think you need to delete gamesettings_saveslot.sav at the SaveGames folder. for me as i was confused i deleted all the content from the folder "Saved", and when i opened the game it rewrite the folder again but the keybind settings reverted to default and i can rebind again, but be careful of changing too much of it cause it will cause the bug again