How was Hashem like an enemy?
Rav Sadya Gaon: He destroyed Beis Yisrael.
Palgei Mayim: He was only like an enemy. "Bila Yisrael", but not all of Yisrael.
How did He swallow Yisrael?
Ibn Ezra: He exiled Shomron (the 10 tribes), and saddened Yehudah.
What is the significance of swallowing the castles?
Palgei Mayim: He vented His anger on wood and rocks, to minimize killing Yisrael.
What is the meaning of "va'Yerev b'Vas Yehudah"?
Rashi: He increased in Keneses Yehudah. Va'Yerev 1 is making something else increase. When Yirev has a Chirik, e.g. "va'Yirev ha'Am" (Shemos 1:20), the matter itself increases. The same applies to all verbs that the last letter of the root is Hei. "Va'Yifen Pharaoh" (ibid. 7:23) - he himself turned. "Va'Yefen Zenav El Zanav" (Shoftim 15:4) - he turned them.
Ibn Ezra: With a Segol, this is Kaved conjugation (Hif'il).
What is "Ta'aniyah"?
Ibn Ezra: The Tav is extra; it is from "v'Anu v'Avlu" (Yeshayah 3:26), i.e. mourning (Ri Kara, Rid).