Alt+F4 and Alt+Enter should work. I just tested it and it works here; I've had others report success. For the UI scaling, that's a lot of work - I think you'll just have to make do with 800px.
Sorry for the confusion. I know they work on keyboard, but I don't often have a keyboard next to me when playing games. I meant add an actual full screen and window toggle and quit option to the options menu.
