I just watched TS1 again (on YouTube!). I saw Jack seem to grab Ennis' hand offscreen, when they're sitting up, and put it somewhere also offscreen. I noticed Ennis settled down slightly at that point and stare more intently into Jack's eyes, as if he's getting it. So I changed my vote to include that.
I also heard, with the speakers pressed to my ears, Jack breathe some sounds that could possibly be "fuck me," or could also just be gasping. I'm not quite sure enough to add that to my vote.
I'm trying to be scrupulously empirical about this!