Just giving it a try on Jaguar XJ220, everything seems to be working great
Modifier keys work, eg to quit back to the main menu you have to hit SHIFT+ESC, I've mapped both of those keys to gamepad controls and hitting both of them at the same time indeed brings you back to the menu.
Pause is a bit temperamental but it appears to be that way in the original game (doesn't always work when you press P, especially if it's for an extended time)