Since it says "Al Bavel", there is no need to say "Aleha"!
Radak: Sometimes a verse gives a pronoun, and afterwards the noun, e.g. "va'Tir'ehu Es ha'Yeled" (Shemos 2:6).
What is the tense of "Chitesah"?
Radak citing Targum Yonasan and others: It is passive (were broken). The Chirik under the Ches is in place of a Shuruk (it is passive). The same applies to "u'Fitechu She'arecha Tamid" (Yeshayah 60:11).
Radak: [It is simple past tense. It is as if Bavel] broke its bows, via its many sins. This is why it says "Ki Kel Gemulos Hashem"!
Why does it say both "Ki Kel Gemulos Hashem" and "Shalem Yeshalem"?
Malbim: Gemul is according to excitement of hatred. Tashlumin is according to the action; he is punished both due to the hatred, and due to the action that he did.
