Why did he say "Al Elokim Yish'i"?
Radak: He will remove me from Galus, in which I am afflicted.
Why did he say "u'Chevodi"?
Radak: I am disgraced in Galus. He will again be my honor, when He will remove me from Galus; all nations will honor me - "v'Hayu Melachim Omnayich" (Yeshayah 49:23).
Malbim: This is kingship. Hashem did not need to make David king - many Tzadikim did not attain honor and kingship in this world - however, He promised so to David.
Why does the verse end "bEi'lokim"? It already mentioned Elokim!
Malbim: Chevodi (kingship) was only because He accepted to do so for me. "Tzur Uzi Machsi" is because He is Elokim - even without a promise, He guards His Chasidim.
