1)
What would have happened if Hashem were not with us?
1.
Radak (1): This is like it says (2-3) - when a man rose against us, they would have eradicated us.
2.
Malbim: They would have destroyed our bodies and souls.
2)
Why does it say "b'Kum Aleinu Adam"?
1.
Megilah 11a: This refers to Haman [who wanted to eradicate us] - a man, and not a king.
