1)
Why should they seek Shalom of the city?
1.
Malbim: They will receive influence via Bavel. They will receive first - "vi'Shlomah Yihyeh Lachem Shalom."
2)
How long will they have Shalom in Bavel?
1.
Radak: It will be as long as the exile lasts. When Bavel is destroyed, they will have more Shalom; they will leave exile.