> I would press ESC repeatedly in Emacs, three of which are enough close a window.

You can configure every combination of keystrokes in Emacs - just bind M-ESC ESC to something harmless (such as, e.g., not function at all).

One possibility would be the following line in your ~/.emacs file:

    (global-set-key (kbd "M-ESC ESC") 'keyboard-quit)