1)
How will they be "l'Za'avah"?
1.
Rashi: People will hear of the evil that came upon them, and shake. Radak - even though it is written l'Zava'ah, this is the same, just like Kesev and Keves are the same.
2.
Malbim: It was decreed that Nebuchadnetzar will chase after them. All the kingdoms that [the remnant of Yisrael] is among them, it will be bad for them, and they will shake.
2)
Why does it say "l'Cherpah"?
1.
Malbim: They will be shamed everywhere, even where Nebuchadnetzar's authority does not reach 1 .
3)
What is "li'Shninah"?
1.
Rashi: Everyone will repeatedly speak about their punishments.