There are 3 flights that connect in GRU for the GIG leg.
dfw-gru, jfk-gru,mia-gru. So they schedule around the arrivals. Yes you can go to the AC. When I was there in Nov. it got very crowded, but a decent club. Some food and open bar. The walk to the connecting flights can be about 20 minutes, depending what gates they use. So even though 2 hours sounds like a lot, it goes by pretty quickly. Though 1-1/2 hours would be better I think. I am doing this run in Feb also for carnival. The mia-gig non-stops are great, but I have found very difficult to use awards on. They seem to push you to the gru connection