What is the meaning of "Hatzileni mi'Damim"?
Rashi: Save me from dying via the sword of the punishment for killing Uriyah ha'Chiti. Radak - Dam can be singular or plural - "Dam Naki" (Devarim 19:10), "Damav Bo" (Vayikra 20:9). Ibn Ezra says, this is because blood is one matter, but it bears all the four 'elements' (earth, fire, wind and water).
Malbim: This corresponds to what the Navi told him that he will pay four-fold [for the sin of Uriyah].
Why does it say "Elokim"?
Radak: You have all ability, and judge everything; You can judge and pardon.
Why did he say "Elokei Yeshu'asi"?
Radak: You will save me from this judgment.
What Tzedakah will his tongue sing about?
Radak: You will pardon me.
Malbim: You will exempt me from the four-fold punishment decreed on me. The tongue symbolizes internal speech - I will contemplate and recognize Your Tzedakah. The mouth and lips symbolize external speech. The Tzedakah is the Tzedakah of Hashem Himself. The praise will be amidst a great Tzibur, that He does Tzedakah, that You do not make me pay based on Mishpat (four-fold).