1)
Why does it mention here that Hashem is Chanun, Tzadik and merciful?
1.
Radak: This is why I call to Him.
2.
Malbim: He heard my Tefilah because (a) He is Chanun, and gives free gifts [to people] without good deeds; (b) He is Tzadik, and will do for me due to my good deeds; (c) Elokeinu has mercy on the poor and crushed. Until now, He always heard my Tefilah due to Chanun and Tzadik; He will continue to hear it due to mercy.