1)
What is the meaning of "Hotzi Hashem Es Tzidkoseinu"?
1.
Rashi: We were remembered in front of Him for merit; the virtue of our fathers came in front of Him. Radak - the verse speaks on behalf of Jews who were in Bavel.
2.
Malbim: Other nations said that Bavel fell due to its Mazal. Yisrael say that it is because Hashem took out our virtue and waged our battle. Therefore, "we will tell in Tziyon the act of Hashem Elokeinu."