I don't see why it has to be either/or. Earthly (literal sense) and heavenly (allegorical sense) can apply simultaneously to the same passage. It's a question of register. At very least, the literal and figurative shouldn't be inconsistent. So when in Gen 1:16 we have a 2 lights, and this is alluded to in Rev 21:23, I'd feel fairly safe that there are 2 literal and figurative lights being taught. To doubt that is to reject that any meaning can be taken from those scriptures, is it not?
Look, buddy (Note: I say these words with a tone of love):
People have seen the stars rotating in different direction on the North pole hemisphere vs. the South pole or hemisphere. Pay close attention to the pic below, and you will see the stars rotating in different directions.
That's observable Science that only works on a globe and not a flat Earth. You can do an experiment at home by putting cameras (or taping your smartphone) on a globe vs. a flat disk like a pizza or something. You have to cheat and put the cameras or smartphone underneath the flat disk in order to make your theory of a flat Earth work.
While the Bible does appear to at first glance make it appear like the Earth is flat, there are tons of other metaphors or other words in the Bible that if taken too literally do damage to our understanding of what His Word is really saying. Context is key. There are verses that support a globe Earth, as well. These verses may be more subtle in expressing this truth, but they are true nonetheless.
Compass Directions East & West and Psalm 103:12.
I am thankful for CF poster "Brad B" for this discovery. He said, I quote:
"...God said He would remember our sins no more that they would be taken away as far as the East is to the West. Notice He didn't say North is to South because each of those positions would have an ending on a globe. However the directions of East and West have no ends on a globe." ~ Quote by: Brad B.
This is from Psalms 103, and it says,
"As far as the east is from the west, so far hath he removed our transgressions from us." (Psalms 103:12).
It is true there are no points for an East or West. However, there are points for a North and South. They are called the North and South poles for a reason on our spherical Earth. But on a Flat Earth, South is outward in all directions on a Flat disk. On a Flat Earth: The South is an infinite circle (sort of like a pizza crust) and it does not have any one ending point exactly. Granted, while God's Word is not a Science book, we should see it line up with Scientific truths because God created the Science of our universe. So when the Bible talks about Scientific things like North, South, East, and West, we would expect to see the truth of God's Word support the physical real world we live on in light of the truth of God's Word; And in this case, Psalms 103:12 makes more sense with a spherical Earth than a Flat Earth.
Side Note:
Oh, and I am also not intending Psalms 103:12 to be the one and only verse that refutes a Flat Earth. I believe it is merely one link in a Scriptural chain of evidences (of which I hope glorifies Jesus Christ).