If you think so, all the delusional scenes involving dead people were really carring us to the 1º interpretation. And so did the first scene where the protagonist holds his beloved dead woman: she clearly had a shot in his torso, not a burnt sking as he later tried to make us think.

By the other side, the third interpretation is all around, every little clue makes you think about sinister intenctions coming from the hospital personel. And, moreover, in the last scene, just note which name the doctor/Chuck uses to refer to his patient/comrade. And, if you remember what the doctor (who was camping in the fireplace) said, just one trip to the firehouse and Chuck would act as anyone he’s been told to be.

So, clues seem to go anyway they want, and the pretty thing is that they dont have to get to the same point. Probably the main character in fact DID find out some inconscious part of his live (now, it could be little, some or all that we’ve seen) and he found it in the worst place in the world: Shutter Island. That would mostly explain why he did not try to get away at all from the island -while convinced it was a conspiracy-, nor even pretend he was sane -the only way to help his friend, get his life back and uncover the hospital’s truth.

It was great seeing you there.

-Jacot