1)
What do we learn from "Hashem ba'Shamayim Hechin Kis'o"?
1.
Radak: He is like a king who sits above everything. If Shamayim is His throne, everything - Shamayim and Eretz are below Him, and in His Reshus.
2.
Radak citing Shocher Tov: There are four haughty ones in the world - the lion is haughty over all Chayos, the ox over all Behemos, the Nesher over all birds, and man rules over all of them - "u'Rdu bi'Dgas ha'Yam uv'Of ha'Shamayim
2)
What is the meaning of "Mashalah"?
1.
Rashi: [His kingship] rules. (Past tense used in place of present.) Radak - this repeats the beginning of the verse.
2.
Malbim: Refer to 103:19:1:3.