A valid interpretation but not the one that naughty dog intended, I think.

She knew that he was lying about the fireflies. So her asking him to swear that the lie was truth was her way of getting Joel to tell her whether or not he is committing to her. Because he would never just say it, it isn’t in his character.

Doubt it, that’s the same idea that the promotional material for the first one implied when they linked shots of an ill pale faced Joel looking up with a shot of Ellie holding a gun looking down. I think Neil is a fantastic storyteller and making these two characters try and kill each other seems straight up…

Based on what we heard, it sounds very Santaolalla-y

Agreed, I don’t know why so many people consider the ending to be a “cliffhanger” anyway. Go back, replay the game, pay attention to the relationship between Joel and Ellie and how it evolves and devolves over time. There’s more beyond the literal words that they say to each other during the games closing scene and…