See, now that I really start analyzing things, it's becoming clear to me that Will never actually survived that bully encounter back on the playground ("Where I spent most of my days"<--- why else would he be speaking in past tense here?)

And that moment where his life got "flipped, turned upside down" actually refers to his death, and the cab ride, Bel Air, etc. are all just metaphors for his ascension to a higher spiritual plane. "Looked at my Kingdom I was finally there"... Kingdom/Heaven, God/Uncle Phil, etc.

(This might also explain why the cab smelled funny?)_