1)
What land is agitated?
1.
Rashi (31): Eretz Yisrael.
2.
Malbim (Derech ha'Muskal): They make the pillars of Beis ha'Nefesh shudder.
3.
Malbim (Derech ha'Pashut): The land of the slave who rebelled and became king.
2)
What is the fourth evil, and why does it say "Lo Suchal Se'es"?