Thanks for the kind comments, TPE, No need to say how much I enjoy all your insights.
to get back to the scene, I like the idea that neither of them has ever had anyone to praise them before, and we all enjoy admiration and approval. Jack's father clearly didn't encourage him, and Ennis's father doesn't sound the sort to have done so either, so how good would it be to be Ennis and have Jack clearly showing his admiration for your skill, and the knowledge that you were able to feed him and yourself?
And for Jack the "dumb-ass missing" is less a criticism than a sign from Ennis that he feels safe enough to joke, and to share laughter with the one you love is a wonderful experience of harmony. How much laughter have they had in their lives? Precious little, I should think.