GTL does have midi learn. It will listen for any midi CC note when you are setting up a midi binding. So you don't need to program the KeyStep, just GTL.
Not sure I'm following with what you want to do with the sequencer, it's early still here!
GTL is designed primarily to be a live looper so the loops will loop round until you tell them to stop. So at present, you can't play a loop once, you will have to manually stop it. You could set up a midi binding with the "Play/Stop" group function. You would need to trigger it once to play and again to stop.
