I pressed fn Ctrl, and F5 and changed the midi device, and now the game wont start. How cam I clear the config so I can play the game again?

The info from the ScummVM maual is likely helpful for you:
http://wiki.scummvm.org/index.php/User_Manual/Configuring_ScummVM#Using_the_configuration_file_to_configure_ScummVM

You have to find a config file "scummvm.ini" (I guess the GOG version might put the file in game folder) then edit midi related value (if thats what caused the problem). I guess removing the file might also force ScummVM to reset to default settings.