yeah - it would seem there is an internal conflict within Rust, but at the same time there is his external ability to influence events which may be real or imagined. I thought it was interesting how his near-death experience was all about to surrendering to darkness, not light. And as he comes into the realm of evil he hallucinates the flash of light. Everything gets flipped on it's head in terms of what is real and what is a twisted reality, and just where Rust's involvement lies within good and evil.
He does tell Marty that he is him. And Marty does serve his interests rather well in the end. He mows Marty's lawn which echoes the scarfaced dude (that unsolved mysteries clip is mind-blowing). The drawings on buildings look like his drawings. There is so much interplay with the mystery that is Rust and the unreliable narration that he provides. What does he hallucinate? What does he make up? What does he lie about? I suddenly want to watch the whole thing over again. Damn.