So in this case the use of "I swear" is used to describe how Ennis feels rather than what he is thinking. So "I swear" means just that and that alone. There isn't any more.
Yes, if you read my first post to open this topic, you will find that one of my first possible conclusions is that Ennis just meant something like, "Why, I declare!" , a simple but heartfelt exclamation like
texman is pointing too, but the fact is, he is speaking directly to Jack... "
Jack, I swear..." and that is not a simple exclamation, it's unusual; and makes people wonder. So while I understand what you're pointing to
texman, I still feel there's more in the "mysterious statement". It is clear that he is "talking directly to Jack" as if Jack were there which seems to indicate there's more to it.
But in the end, the line is open to almost any interpretation and so is what lies ahead for Ennis. In another thread that asks us to write the future for Ennis, I wrote something like,
He gets help, comes out, moves to Denver, meets a guy similar to Jack, falls for him, struggles, dates, the guy falls for Ennis and they end up living together, not happily ever after, because that isn't real life, but he finds a partner to share his life with... and that's the end, as good an end as any.
It's fiction, anything is possible.
Peace,
Rayn