Interesting discussion here!
I for one don't cut John Twist any slack on the "he resents Jack for not staying to help with the ranch" for several reasons. I also don't think Jack and Ennis moving to the Twist place would have worked out, either.
(1) Expecting a child to not break away from the nest and build their own lives is the action of a selfish parent. And resenting them bitterly for decades for having done so is stinks of jealousy and bitterness. Anyone who cares to look (and are old enough to have lived life a little while) has seen the type of stunted adulthood this type of parental expectation can produce.
(2) If John hoped that Jack would choose on his own to stay around the ranch, he should have fostered a better relationship with his child. From the glimpses we have of the Twist home life it seems like just the opposite...the type of place where most any type of child would want to leave as soon as they could walk.
(3) John Twist couldn't get help because he was too remote? "Remote" is a very relative term in a place like Wyoming. Several miles between neighbors is nothing. Sometimes just to get to the buildings from a public (dirt) road is a couple miles. And in the perpetually-economically-depressed open west, ranchhand work had to be pretty awful for nobody to take it back then. Look at the remote, lousy, unsteady work that Ennis and Jack took just to have a job. If John Twist couldn't get help, I suspect he either paid nothing, offered terrible conditions, or both. Probably doesn't take too long to get a reputation.
(4) If Jack did stay at...or return to...the Twist ranch, what kind of life would he have had? His parents were dirt poor and don't appear to be making it on that ranch. Would it have been able to support Jack and Ennis or someone else as well? And would John have let Jack take the ranch over? Doubt it. I come from a farm background and have seen people like John Twist plenty. They expect their son to be their hired man until they drop dead...be loyal and work like a dog as the father gets older and can do less, but won't sell the place to them. The son gets to be 40 or 50 or older and doesn't own a dang thing to show for their years of hard work. Don't control anything, don't get to make any decisions. Their only hope is that the old man dies while they are still young enough to get something out of it. Assuming the old man's decisions and ways didn't drive the place in to the ground in the first place, there might be something to inherit. Seen this very thing happen many times. Breeds hate and resentment. And I can think of several instances where the son's marriage was busted up by this very situation. The daughter-in-law resents her father and mother in law for not letting them build their own life, and she resents the son (her husband) for letting himself be pushed around by his father. Jack and Ennis live happily ever after with the Twists? I think that's a long shot.
(5) I think that John Twist is dripping with disgust when he talks about his son wanting to build a cabin and live with a man. Right from the first moment he says "Ennis Del Mar". If he really wanted this (so he'd have help) his contempt would be sharpest when he says that this was just another half-baked plan of Jack's. He might even have sounded wistful, positive or at very least neutral about Jack's plan to come home with another man to help out on the ranch, then turned sour at the "but it never happened" part. I don't hear any of that. Rather, I think John Twist is coming from his own perspective where men don't live together unless they are queers, and that's just wrong and disgusting. Everybody knows that, and it sickens him to think that his own son was one of them. As for Mrs. Twist, well, it's hard to know exactly how she would have been if she actually had to face facts right up front. When we meet her, years had passed and she had a lot more time to get used to the idea, versus if Jack just showed up at 19 or 23 with Ennis one day and they lived together. Also, when a loved one dies, it's very common to have a change of heart about things. In her grief and longing for her son, Mrs Twist showed great compassion and understanding for her son's lover. No guarantee she would haver reacted as supportively if instead Jack and Ennis showed up and started bunking together.
(6) I doubt that Ennis would have accepted the remoteness of the Twist place as any kind of comfort to allow him to live with Jack. Ennis would have had to stay secluded on the Twist place for years -- never go to town, never go to the doctor, or dentist, or a movie, or to vote, or to or buy anything. Why would he have to do this? Because word gets around quickly in a rural community. Even if Ennis got mail the local postmaster or postmistress would know that Ennis lived with the Twists. And from local experience growing up in rural areas in the 70's and 80's, they gossip. Maybe nobody would have hassled Jack and Ennis, but the critical thing is that Ennis believed that. I don't think the Twist place would have offered the level of security Ennis needed. Heck, I don't think he would have accepted living in a cabin up in the mountains, either. It wasn't only remoteness but "appropriateness" that allowed him to be comforable with Jack. Two guys camped together for fishing or hunting? Nothing unusual about that. Two grown men living together, just the two of them? No good way to explain that.
I do understand the line of thinking followed in some of these threads, but I run into roadblocks following it. And so I view it a little differently.