Comment: Shotgun approach? :)

Slavery:

"He who kidnaps a man, whether he sells him or he is found in his possession, shall surely be put to death." (Exodus 21:16)

This seems to be a good summary of the topic:
http://www.godandscience.org/apologetics/slavery_bible.html

Age of the earth:
Where does it say '6000 years'? That is one theory, based on folks trying to calculate years from genealogies, etc; but it doesn't state an age of the earth explicitly. And anyway, no length of time from the end of Creation to the expulsion from Eden is given.

Four corners:
Come on -- that's just a figure of speech. CS Lewis wrote whole stories using the Medieval view of the nested spheres of the planets and cosmos, knowing full well they were not really that way. We still use phrases like 'the four corners', 'the sun moved across the sky', 'the seven seas', 'where east meets west', etc., etc.

Check out Isaiah 40:22, Job 22:14 if it is roundness you seek. Job 26:7 for possible reference of Earth 'hanging' in space.