Ff first steps: how far were they going to move the earth?

He explicitly states that he found other candidate stars around which the Earth could be places. So just like we observe and know how some star systems are composed in great detail, it stands to reason that the man who solved FTL travel also has detailed knowledge of those candidate stars.

At no point was it ever stated that he'd just randomly teleport somewhere

As far as the plot required.

Its covered directly in the movie

Space is not mostly empty.  "Cosmic Dust" and matter that weakly or does not reflect light that we can detect is a thing.


Reed's plan would not work.  Teleporting the earth, *if* it didn't get destroyed by some matter he couldn't see, and *if* it didn't change the orbital configuration of the other planets causing a death spiral collision with another planet, still would have been obvious.


The gravitional pattern of the target star would change, and the light pattern would change with a new obstructing body in place.


All Galactus would have to do is see which star changed at the same time Earth disappeared and go there.