What do we learn from "ba'Tzar Li Ekra Hashem"?
Malbim (Tehilim 18:7): Amidst affliction, I need Tefilah and to call to Him amidst the affliction. I will pray to Him for salvation; He will hear my voice from His Heichal, and rush to save me. 1
Malbim: [The theme of] this verse is repeated throughout this Shirah. Here he discusses salvation via natural means. When he calls to Hashem amidst his affliction, Hashem prepares a natural salvation. However, this Sibah (way of salvation) itself causes (via nature) another affliction. He prays, and Hashem saves him through another Sibah, which leads to another affliction
Why does it say "Ekra" (future) and "va'Yishma" (past)?
Rashi: Sometimes present tense speaks in the past and future at once.
What is "me'Heichalo"?
Radak: It is from Shamayim.
What is the meaning of "v'Shav'asi b'Aznav"?
Radak: My cry comes in His ears. And so it says [in this Shirah] in Tehilim (18:7) "Tavo b'Aznav."