David - I agree that Jack lost a lot of hope after the 'divorce' scene and we don't ever see either of them smiling & relaxed again w/ each other, but Jack continued to try and move Ennis forward throughout the film:
"You going to do this again next summer?"
"What are we goina do now?" (Motel scene)
"It could be like this, just like this always"
"You & Alma, that's a life?"
"Got your message about the divorce...I thought it meant ..."
"Maybe you should move somewhere else, Texas maybe..."
"Live your f...ing miserable life, I was just thinking out loud!"
"You ain't found someone else..."
"Sometimes I miss you so much I can hardly stand it."
"I did once." (Resignation, but what if Ennis had responded differently)
And, even when Ennis cried, "Get the f... off me!" Jack held on tight & again said, "It's alright, s'alright"
I agree that Ennis was almost there after the lake scene. I also think the November meeting would have been 'IT' - one way or another.