...and for another POV...
There are at least two main reasons why many people think that Ennis does Jack wrong: 1) he never says I love you; and 2) he won’t move in with him. Of course there are many probabilities for these behaviors, but, having been an Ennis myself – not recognizing what I had, not believing that the good in my life was there on purpose or that I deserved it; and never a good enough opinion of myself to live up to my own promise – I more likely than not see him through different eyes.
Ennis never tells Jack he loves him because until Cassie defines “love” for him, Ennis does not know how to name what they have other than this “thing” because he honestly is incapable of knowing what it is. The “Earl” experience caused little Ennis to retreat into his own head because before he trusts anything, before anything becomes real for him, he must have the experience of it, and that does not assure him that he will be able to name it. He’s never seen how a loving couple behave, certainly not a loving couple of men – he honestly doesn’t know that these strong feelings and desires are love, and doesn’t trust thinkin’ about it. He knows sex because he's grown up around animals and seen them doing it every day of his life, but he has no idea that this yearning to be with Jack, and have the pleasure of being in his company is anything other than a strong sex drive. The love is there in encompassing depth – look at what Ennis does for Jack: everything his heart desires that Ennis can do except the one thing that Ennis knows from experience will get one or both of them killed – and Ennis doesn’t talk about love, he's not sure that that’s what this “thing” is, but, hell, Ennis didn’t say a word for the first 6.5 minutes of the movie, but he kept up his end of the dialogue with gestures and expressions instead of talking. His gestures of love to Jack just happen to be doing whatever Jack wants, but one.
Ennis knows that death to queers can come randomly and suddenly, and you’re not only dead, you’re the joke of town. And that is reason #2, the trauma caused little Ennis to realize that all the “thinking” in the world cannot protect you from people who don’t like men who ranch up together. He gives up thinking and turns it into a curse: “You’re a real “thinker” there, Jack F*ckin’ Twist.”
That he doesn’t know how to talk about it is a product of his exposure to people, or actually, the lack of it. He had no role models: Mom and Dad dead, sister gets married and doesn’t look back, and bro throws him out when he gets married. Jack Twist is the first person in his life he’s met cold, with nobody in his family knowing him ahead of time. Ever wonder why he answers just “Ennis” when Jack asks his name? He’s never had to introduce himself to anyone ever before in his life, at 19! Until now, somebody older has already given the family name, or it's already known. He’s shy and withdrawn; Jack’s outgoing and talkative, and sympathetic. This is gonna be all right. Ennis is on his own for the first time in his life; Jack’s been down this road before. Ennis has skills; Jack tries. Jack entertains and draws Ennis out of his shell (and may be the first person who’s tried); Ennis protects and provides for Jack. They fit together and both recognize this fact and don’t mind it a bit, but neither of them will call it by its name any time soon. Ennis doesn’t know what it is, and Jack’s the center of Ennis’s attention, so he doesn’t need to know its name – he’s got it, whether he knows it or not, and doesn’t need to know how to call it or not.
Ennis knows he’s got it in abundance, but can’t name it and so can’t tell it; Jack has it in abundance but doesn’t know it, and so he needs to hear the name of the gift from the giver. They unwittingly bar each other from the gifts they've already shared.