Will they dwell only in Yerushalayim?
Radak: It mentions Yerushalayim like I explained (3) because it is the capitol, and due to the Beis ha'Mikdash - all of Yisrael come to there.
What are the consequences of being Elokim to them?
Malbim: I will unify My Hashgachah on them - on condition that it is "be'Emes uvi'Tzdakah." If not, it will be wondrous to do this (i.e. I will not do it). It can be only via miracles, and miracles are only if they merit via their deeds.
Why does it say "be'Emes uvi'Tzdakah"?
Radak: This is like "v'Erastich Li [b'Tzedek uv'Mishpat uv'Chesed uv'Rachamim; v'Erastich Li] be'Emunah" (Hoshe'a 2:21-22).
Malbim: They will do Emes Bein Adam l'Chavero and Tzedakah Bein Adam la'Makom. Refer to 8:8:2:1.