What is "Kir"?
Rashi: It is Yerushalayim 1 .
Radak (16): The first time (12), Yonason translates Kasla (wall). Afterwards, he translates Karta (city).
I do not know why Rashi did not explain this above (12). (PF)
What is the meaning of "Asher Tachtem"?
Radak (16, citing Targum Yonasan): You prophesized in it false Nevu'ah.
Why does it say "v'Harasti? v'Higatihu El ha'Aretz v'Niglah Yesodo"?
Malbim: Respectively, these refer to (a) fragmentation, so it is not complete ? this is breaching the city, (b) totally falling, and (c) the foundation is revealed. There will be no remnant.
Why does it add "u'Chlisem b'Sochah"?
Radak: The false Nevi'im will be killed.
Malbim: Do not say that only the wall will fall, and people will not be harmed. The wall will fall on people!
What will inform "Ki Ani Hashem"?
Malbim: The wall will fall on people.
The anger will consume only on in Yerushalayim and the false Nevi'im, but not Klal Yisrael (PF; Malbim 15 says so).