I love the golden bowl metaphor here--so appropriate.
I think it's important for us, too, to see Jack's imperfections. After reading the many threads here over the past 5 months, I feel like Ennis sometimes gets more of the blame than he maybe deserves. He wasn't perfect, but neither was Jack. They were totally human, with human frailties--and that's why we love them, and why they love each other, so much.
On a more personal note, I do wish that Jack hadn't been unfaithful to Ennis--but I also wish Ennis had been willing to try a life together with Jack. So it goes.