I just towed my 2014 Acadia 1200 miles for its first trip. I pulled the same 3 fuses: BATT1, ECM, and Onstar. I'm not sure if the 2 in the battery compartment are a battery drain issue or more of a computer/communication issue.
But when I went to start it after being on the road for 7 hours or so I had a dead battery. I had to go buy a portable battery pack jumper and got it started. I hadn't noticed that the high beam headlights were on in car as we were going all day. I pulled the 2 10amp fuses for high beams, and we were good to go the rest of the trip. I don't understand why or how they were on, but they must have been the culprit.
Also, the check engine light stayed on after we reached our destination and drove the car. After the 2nd or 3rd day of driving it, the light went out. A GM service tech at local dealer said that was probably from removing the ECM fuse. The computer had a communication disruption with the rest of the car, and it took some time for it to reset itself, or something to that effect.