1)
Why does it say "Gam Bavel... Gam l'Vavel"?
1.
Rashi: Bavel caused bodies of Yisrael to fall [dead], and so will fall its entire land. Radak #2 - it is as if it says b'Vavel. Also "va'Yeshvu la'Aretz" (Iyov 2:13) is like ba'Aretz. "Haragti l'Fitz'i" (Bereishis 4:23) is like b'Fitz'i.'
2.
Radak #1: This explains why all its bodies will fall [dead - verse 47]. It is because it made bodies of Yisrael, and of the entire land, fall.
3.
Malbim: Because Bavel is prepared for bodies of Yisrael, and of the entire land, to fall there, therefore leave and do not stay (verse 50).
