I pretty much agree with your overall caution about JG--it's silly not to be cautious about a guy who's played a game and a half. Pig in a poke! But I do have a quibble with this point, which you've made a few times.
I don't think you can really say Miami was "starting to figure him out." His first three drives went for TDs and he had 3 incompletions total on them, as Miami went 3 & out three times. The Pats would have won about a 100 to nothing if that kept up, so it's obviously not sustainable.
On the next Pats' drive he had a couple of incompletions and the Pats punted. Happenstance. The next two drives, he drove the Pats to the Miami 42, first down, and Amendola fumbled; and on the drive he got hurt, they were on the Miami 21, first down. He had a couple of incompletions on each drive, but was still leading the team down the field.
Again, it’s not even a full game, all caveats apply. But the “figuring him out” thing seems like a misread.