Just a general comment on the 'restrictions'. I've pointed out before that the things we are initially told are ambiguous enough, that we could see them as pointless - that we're just being told about the normal expression of sex between men that age. But for those who think that that's all they mean, why do you think we are told them? As I mentioned about other sex (e.g. Jack and Lureen), if there's nothing we need to know about it, we're not told. So why do you think it's so important that we must know exactly what they did in the FNIT, that they didn't talk about it at all, that they didn't say a word during sex, that it was all quick and rough, etc. Because what I see is people saying that it could be that way for men that age, but not really explaining why they think we're given that precise detail.
I also disagree that all quick and rough, etc. is the norm for men this age. I most of us will at some point (even if it was a while ago) have had lovers that age, or inexperienced lovers - given time (which Jack and Ennis) and lack of inhibitions, they are usually eager and keen to explore. Maybe personal experience affects your view on this a lot, and maybe I've just been lucky. But if they're limiting themselves to quick and rough sex, and we know that time and privacy aren't an issue, I think we're left with the lack of inhibitions - they are inhibited. Now that might be normal in the circumstances - I'm not saying it's not - of two men from that homophobic background who need to prove they are straight, macho men while having sex. I'm not saying that what they do is particularly weird, because if it was, we wouldn't have accepted it on first reading of the Brokeback time - it's normal enough. It's also normal enough for Jack to believe that there's the potential of more. But it's still a restriction - they're inhibited by their need to be masculine and appear straight.