I made a joke character to just test the game out and now I actually want to play. It seems you can only have one save, the game tells you to run install if you try to make another. I have tried deleting the app package and reinstalling but I still get the error.

Removing the App doesn't do anything on Mac (if the app was done properly), personall settings like preferences and savegames are stored ine the Library. To reset a Boxer port all you need to do is File -> Reset Game Data in the menu bar or the app.