What is "Ma'aravah"?
Radak #1: The Hei is not a feminine pronoun, for there is no Dagesh. Rather, Ma'aravah is a feminine form, just like Ma'arav is masculine.
Radak #2: The Hei is a pronoun - [west of] the sun; sometimes Shemesh is feminine. Sometimes there is no Dagesh, even though it is a pronoun.
Why does it say from east to west, but not from north to south?
Radak: The entire world is settled from east to west, but not from north to south (people do not live at the north and south extremes of the world).
Malbim: Everyone recognizes east, from when light starts to shine, and west, where the sun sets.
Why does it say "Ki Efes Bil'adai... v'Ein Od"?
Malbim: There is only Me, the source of good. There is no source of evil and darkness.
