1)
How will the city be to Hashem?
1.
Radak: It will always be to Hashem; it will not be destroyed again. It will be wider, according to the new borders given here.
2.
Malbim: It will no longer be of Yehudah and Binyamin, rather, to Hashem. It will be Terumah to Hashem, like it says in Yechezkel (48:8), and it will be Kodesh to Hashem.
2)
What is "Sha'ar ha'Pinah"?
1.
Radak: This is Sha'ar ha'Pinim. And so it says in Zecharyah (14:10) "Ad Sha'ar ha'Pinim." Also there it mentions Migdal Chananel. Chananel was a name known to them. Targum Yonasan [of Chananel] is Pikus.
