1)
For what "v'Yiten Es Yisrael"?
1.
Radak: The verse is abbreviated; they will be for a curse and a source of astonishment [for those who see their afflictions].
2.
Malbim: He will punish them also for Chatas Yaravam. Since they will add to make Asheros, this shows that they were pleased with Yaravam's actions; they were not forced.