What is "Tif'eres Uzamo"?
Radak: It is the glory of their strength. They had no strength other than You; in Your strength, they boast over the nations.
Malbim: Oz is natural strength. Tif'eres does not apply to a person's natural strength. One cannot boast about a natural attribute. Gilah does not apply to it at all. However, Yisrael boast about their natural Oz, since it is via Hashem's Hashgachah. It testifies that they are His special, Kadosh nation. This is why they have Gil the entire day!
What is "uvi'Rtzonecha"?
Rashi: It is Hashem's satisfaction.
Malbim: It is Hashem's desire. This explains why "uv'Tzidkasecha Yarumu" (verse 17). The Divine Tzedakah via which He does wonders, without looking at the recipient's merit. It depends on His pure desire.
Why is it written Tarim, and we pronounce it Tarum?
Radak: The Kesiv teaches that You raise our horns. The pronunciation teaches that our horns are raised. This is like "Ramah Karni ba'Shem" (Shmuel I, 2:1).
Why does it say "Tarum" (singular)? "Karnenu" is plural!
Radak: He raises each horn, i.e. each king of Yisrael.
