I think that the mechanics of the movie dictate that Salieri gives up his narration to an omniscient narrator in between sanatorium scenes.

Yeah, I won't press too hard upon my first point because definitely a ton of movies include scenes the narrator couldn't know about and it's not intended to mean anything special.

Do you have no thoughts about my second point? xD Thinking about it again I guess this is the only real argument I have about Salieri maybe being an unreliable narrator, haha.

Unrelated, I totally want to write something now that involves an unreliable narrator. xD It seems really tricky though!!