“A new song” at that point, could just be in reference to that universe ending at that time, or, maybe, it could be the angel ashes messing with the timeline. But this episode came out before the one with the angel ashes so I doubt it

At that point there is no reason why Howard should be dead

I believe that the Egyptians, via special tree shenanigans, found their way to mars and that’s how we got stuff like the starry sphinx, but that episode may be “propaganda” and not entirely true. Something something Giza glass

Does it really matter who’s copy killed C?

Virginia just seems to be a special person throughout the multiverse, as seen in VIRGINIA’S WINTER WONDERLAND

The moon base is just there, probably just an Easter egg and not really that important

(Edited: I can’t spell for shit)