What are "veha'Matim Akalkalosam"?
Rashi: They are those who make false evil accusations against people.
Radak #1: They are Yisraelim who make their ways crooked.
Radak #2: They [appear good, but they] are crooked in their hearts.
Malbim (4-5): Akal is something straight, but it appears crooked. Those who judge unfavorably those who [have straight hearts, but] appear evil, as if they are truly evil, Hashem will punish them as if they themselves do evil.
What is the meaning of "Yolichem Hashem Es Po'alei ha'Aven"?
Radak: Hashem will lead them to evil Goyim.
Why does it say "Shalom Al Yisrael"?
Radak: This refers to those who are straight in their hearts. Since the Resha'im of Yisrael will be eradicated, there will be Shalom on those who remain - "v'Hish'arti v'Kirbecha Am Oni va'Dal v'Chasu b'Shem Hashem", "She'eris Yisrael Lo Ya'asu Avlah v'Lo Yedabru Chazav..." (Tzefanyah 3:12-13).
Malbim: There will always be Shalom on Yisrael, since they trust in Hashem, and it is proper that their Shalom never falter.