1)
What is the meaning of "Im Avonos Tishmor"?
1.
Malbim: If You will not pardon.
2)
Why does it say "Mi Ya'amod"?
1.
Radak: We will almost perish.
2.
Malbim: Who can last? Since Hashem has no limit, also service of Him must have no limit. The smallest sin is very great. One cannot fulfill the obligation to serve Someone unlimited, unless also he is unlimited!