Why does it say "Mi ka'Shem Elokeinu"?
Radak: It is because it mentioned Shamayim, and some Goyim, their gods are the legions of Shamayim. The verse says that none of the gods of the nations are like Hashem Elokeinu.
What is "ha'Magbihi Lasheves"?
Mesilas Yesharim (Perek 25): He oversees everything, big and small. Nothing is hidden from His eyes, not due to greatness of the matters, not due to its smallness. He sees great and small, lowly and honored.
Why is there a Yud at the end of "ha'Magbihi"?
Rashi: It is extra. The same applies to the Yud at the end of ha'Mashpili, Mekimi, Lehoshivi and Moshivi (verses 6-9). Radak (7) - this is to make the expression clearer.
Where does He dwell?
Rashi: In Shamayim.
Radak, Malbim: He dwells above Shamayim, above all upper beings.