1)
What humbles them?
1.
Radak: The toil of captivity humbles their hearts that were haughty and disgraced Hashem's word.
2)
Where did they stumble?
1.
Radak: In captivity.
2.
Malbim: Hashem put a stumbling block in front of them, so they will be incarcerated.
3)
Why does it say "v'Ein Ozer"?
1.
Radak: No one other than Hashem can save them, therefore they call to Him.
