1)
Why does it say "mi'Tziyon"?
1.
Radak: The honor dwells there, in Yerushalayim, and from there comes instruction to all to fear Him, bless Him and honor Him.
2.
Malbim: The Brachah ascends from Tziyon, and according to Tziyon's merit it descends, for Hashem dwells in Yerushalayim and oversees the deeds of its residents. He blesses them according to their deeds and their Avodah in Kodesh.
