1)
How did Hashem help him?
1.
Radak: He stood for me against them. They wanted to eradicate me, but they could not.
2)
What is "Dumah"?
1.
Rashi: It is silent. Malbim - I was silent, thinking that no one can save me, if not Hashem.
2.
Radak: It is cut off, like "k'Dumah b'Soch ha'Yam" (Yechezkel 27:32). Perhaps it is a noun - my Nefesh almost rested in the cut off place, i.e. the grave.
3)
What Nefesh is discussed?
1.
Radak: This is Nefesh ha'Chayim (that also animals have); the intellectual Nefesh does not dwell in the grave.