Why did he say "Hikisa" (past tense)?
Radak #1: Many times You saved me and struck my enemies. Do so now!
Radak #2: He discusses this war. He uses past tense amidst confidence (it is as if Hashem already struck them).
Malbim: You already struck my enemies (refer to 3:8:4:2). Save me (from the rest of Avshalom's troops)!
Why did he say "Hoshi'eni Elokai"?
Malbim: You are Elokai - Your special Hashgachah is on me, to save me.
What is striking on the cheek?
Rashi: It is a blow of disgrace - "Yiten l'Makehu Lechi [Yisba b'Cherpah]" (Eichah 3:30), "ba'Shevet Yaku Al ha'Lechi" (Michah 4:14).
Rashi citing Midrash Tehilim 17: It is hitting on the mouth - "va'Ytzav El Beiso va'Yechanek" (Shmuel II, 17:23).
Whose teeth did Hashem break?
Radak: It is the ones who wanted to tear David - "va'Ashabrah Mesal'os Avel" (Iyov 29:17).
Malbim: David's enemies, through annulling Achitofel's counsel, and he was choked,
