1)
Why should Hashem's anger catch them?
1.
Radak: It is lest they be able to escape Your anger.
2)
What is the difference between Za'am and Charon Af?
1.
Radak: Za'am is the curse, and Charon Af is the anger. The verse depicts that one who is ready to afflict the sinner is the staff of Hashem's anger. The affliction themselves with which he afflicts them is Za'am - "Hoy Ashur Shevet Api u'Mateh Hu v'Yadam Zami" (Yeshayah 10:5). He requests that Hashem pour on them His Za'am and anger, and Charon Af, the Shali'ach to put the curse on them, should catch them.
