1)
Does "Ki" give the reason?
1.
Radak: Yes - since I do not call for help to another, only to You, therefore, have grace on me.
2.
Malbim: Yes - since I call to You the entire day, You should answer me.
2)
What is "Kol ha'Yom"?
1.
Rashi citing Shocher Tov: The entire Galus, which is day for the nations and night for Yisrael.
2.
Radak: Constantly - all days. The same applies to "Osecha Kivisi Kol ha'Yom" (25:5).
