1)
Why is He called "Kel ha'Shamayim"?
1.
Rashi: He prepares food for every creation.
2.
Radak: Rain comes from Shamayim, and it is the cause of all food - "Ki Ka'asher Yered ha'Geshem veha'Sheleg Min ha'Shamayim" (Yeshayah 55:10), i.e. from high in the air. Hashem commands rain to fall from Shamayim.
3.
Malbim: He conducts the Ma'arachah. The primary food and good come from Him. It is all from His Chesed, which is constant.
