1)
Why does it say "Karavti Tzidkasi"?
1.
Rashi: From now, it will not be far.
2.
Malbim: The Tzedakah, that Hashem will atone for Yisrael's sins, and He will reckon their merits, is close. Therefore, "Teshu'asi Lo Se'acher."
2)
What is "Tif'arti"?
1.
Radak: The salvation that I will give to you will be glory for Me.
2.
Malbim: I am glorified via Yisrael's good deeds.