Apologies for the issues! Unfortunately I haven't seen that error before, but based on the message it sounds like Quick Play can't find the executable it needs to run the game. If you look in your RPG in a Box installation folder, is there an "export_templates" subfolder with files inside it?
Regarding the file deletion issue, are the error messages displayed within RPG in a Box or in your file explorer? It sounds like that may be an OS issue. If you haven't already, you may want to try restarting to see if that allows you to delete the folder completely. Hopefully that helps!