Amazing--especially since Ennis is the one to reach out. Yay! 
I did notice the reach over, if you will. Such a contrast to when Ennis recoils when Jack tries to tend to his wound after Ennis falls off the horse. They definitely have built a rapport and a trust, as we see in the next scene when they start joking around. Then comes the "Water Walking Jesus" scene and the flirting, the booze, and well, we all know a certain tent that went rocking after that! 
I love how you described the sequence of events going on that day and into the night...
You know what, I don't exactly see it as Ennis "recoiling" from Jack trying to tend to his head wound. I mean, he does pull away, but he isn't like adamant about pushing Jack away, like he didn't say "what the f**k you doing" or anything like that and get up and stomp off. He just wasn't comfortable being nursed like that, probably no matter by who. But I think he liked that Jack did it, liked that Jack stayed nearby while he did it himself.
But yes, by this day we're talking about, things are so much easier between them, easier for Ennis. Beautiful. Can't you see him falling in love about this time -- probably he'd never been so easy...and so stimulated...around anyone else before. And what a beautiful man to be easy with, is Jack.
kathy