Good topic, David! And good idea to poach promising topics from the old board.
Ennis' tone really captures his lack of enthusiasm for the relationship. Not just the "but I don't know," but also the "wants to be a nurse or sumpn." Like he has barely paid attention to her talk about her plans. Some have said the news makes Jack jealous, which is why he responds with the lie about the ranch foreman's wife. But it's hard to believe Jack doesn't pick up on how blase Ennis sounds.
And my opinion is that, yes, by this point Ennis has realized that he is gay and has partly come to terms with it. I know many people find this view debatable, to say the least. But he seems so unexcited and passive about Cassie -- far less so than he was about Alma, even. He gets dragged into the relationship because Cassie came on so strong and he figures that's what he's "supposed" to do. But when he breaks up with her, it's because he realizes there's no point in keeping up the pretense.
And while we're on the subject, I've wondered if there's any deeper significance to Cassie's "girls don't fall in love with fun." I saw an essay on the old board about this; it was interesting but I didn't agree with the author's point (he was arguing that in the end Jack decided to break up with Ennis as a favor to Ennis and somehow the question of Ennis being "fun" or not worked into it). But given that this line is given such dramatic emphasis and is actually the first time in the movie the word "love" is used -- not, as is sometimes claimed, in the final scene with Alma Jr. -- you'd think it must mean something.
