Why not just quit the PC game as per normal, E.G press exit on the game?
What I read about that, not every game will exit back to AM anyway, that they will still run in the background. It is only if the game allows you to set up a hot key to quit the game.
I cannot really help you further as I have not started on my PC section, I am still slowly adding systems to my AM build, now that I know that I want to stick to AM rather than use another frontend. Once I start getting up to speed then I will know a bit more than I do now, so hopefully someone will read this and help you more than I can.
Regards
Mark