the 1,2 p start button exit thing does work, I use it to exit all my emulators when i'm testing various things. Until I configure DK to run with Zinc, I'm currently using Zinc Gui and I can exit using the 1,2, p start button thing.
Unless you don't have your I-pac set for mame....it should work as escape on anything, because that's what the encoder sends to the pc when those 2 buttons are hit.