Once again, I believe one of the main points of the film and story is the detrimental effects of internalized homophobia. Ennis was a gay man who hated being gay, couldn't accept it because he was taught since he was a child that it was the worst thing in the world. To not understand that is to fall into the same trap that Ennis himself fell into. The inability to accept himself because of the severe stigma attached to it. He was a deeply closeted gay man, and it was the society he was born in and lived in that made him that way. He represents the millions of gay men that have struggled against themselves just for being who they are, desperately trying to be "normal", wishing they can just pray being gay away...it's a tragedy. "Ever get the feelin..." is another tacit recognition by Ennis. Deep down inside, he knows who he is, but can't reconcile the fact within himself. Just like he understood the relevancy of the Earl and Rich story, just like he knew if his father walked in that door and saw him naked in bed with a man, he would beat him to death with a tire iron. On some deeper level, he knew the truth.
As time went on, people around Riverton knew about Ennis. It's a small town, where everyone knows your business. It would have been impossible for there not to have been rumors about Ennis after his divorce from Alma, because I am sure she told Monroe, and especially after that Thanksgiving fight. So I don't think it was Ennis's paranoia. I think people did suspect, hence when Cassie came, even though it's obvious he didn't want her, he relented and started to date her. She was a good cover and although he didn't want her, he could stand her. It was after the last meeting with Jack that he realized and therefore broke up with her by deliberately ignoring her. This is why I believe Ennis was finally going to agree to Jack. If Jack had lived till November, I think Ennis would have finally accepted his proposal.