[Coldsaturn]

You are absolutely right and that was a huge lapsus of mine. The supernova is them looking at the past, which still checks out with the fan theory.

Philos is in the future and the backtrackers travel back in time to Earth, that's canon. What isn't clear is if Philos is an entirely new planet that was colonized after the Earth died or if it's still planet Earth but with a new core.
I'm currently of the idea that the wormhole is a literal wormhole connecting two distant points in the spacetime continuum. The point it connects to could be the past, just like it could be the future, based on how you're folding the universe. I'm inclined to say we're looking at the future because Xavier and [redacted] travel back in time through the tunnel (and it's established that Philos is future!Earth).

To that you have to add spacetime fragmenting itself into multiple overlapping timelines.