1)
Why does it say "Omar la'Shem"?
1.
Rashi: I say to Hashem [that He is my refuge], and all will learn from me.
2.
Radak (2-3): He calls to the Chasid, one who dwells in the hidden place above, and lodges in the shade of Shakai. I speak to you about Hashem. This is like "Imri Li Achi Hu 1 " (Bereishis 20:13).
3.
Malbim: I am His Shali'ach; I speak on behalf of Him.
1
Ibn Ezra: This is like "va'Amar Pharaoh li'Vnei Yisrael" (Shemos 14:3) - about them.