What is "Tzadu [Tze'adeinu]"?
Rav Sadya Gaon: They made desolate 1 . Ri Kara - they made our steps desolate from going in our streets.
Rashi: Enemies ambushed our steps, so we could not go in our streets. Tzadu is like "va'Asher Lo Tzadu" (Shemos 21:13), "v'Atah Tzodeh Es Nafshi" (Shmuel I, 24:1).
Radak: It is as if they trapped our steps. Those whom we hoped for (Egypt and Ashur) they came only to trap us.
Palgei Mayim: Our enemies trapped us suddenly.
The Targum of "Shemamah" (Shemos 23:29) is Tzadya.
What is the meaning of "Karav Kitzenu Mal'u Yameinu Ki Va Kitzenu"?
Ibn Ezra: Our days of serenity in our land 1 finished; the time came for us to be exiled.
Palgei Mayim: Hashem brought close the time of our exile. We should have been in the land 852 years, the Gematri'a of "v'Noshantem" (Devarim 4:25), and then the next verse "Avod Toveidun" would have applied. Hashem's Chesed exiled us two years earlier, to prevent this (Sanhedrin 38a).
It seems that this is his intent. Perhaps the text should say 'Shalvasenu' (PF).