The way I had it explained to me by a friend who’s into his comics (I’m not a comic reader) is that his regen abilities + cancer basically damaged his brain and made him insane which is why he “thinks” he’s a comic book/movie hero. Not so much that he’s breaking the 4th wall but that he’s talking at it like a crazy person. He even has multiple personalities that I wish they’d introduced in DP2! It was hinted at when he’s reunited with Vanessa in DP1 when he says “and now the moment I’ve all been waiting for”