1)
Why does it say "Ki Rotzeh Hashem b'Amo"?
1.
Radak: It is more proper for them to praise than any other nation, for He desired them above all nations.
2.
Malbim: Hashem desires the nation in general.
2)
Why does it say "Yefa'er Anavim bi'Yshu'ah"?
1.
Radak: His nation is humbler than all others, and more glorified via His salvation of them.
2.
Malbim: The humble [in Yisrael], who are the Tzadikim, He will glorify them with salvation. He will be honor for them - "uli'Chvod Ehyeh b'Sochah" (Zecharyah 2:9).