1)
What is the meaning of "Im Amarti"?
1.
Radak: If I thought [that I falter in Galus].
2.
Malbim: It seemed to me that I already faltered and fell.
2)
Which Chesed of Hashem does he discuss?
1.
Radak: It is the Chesed that He did with Rishonim, and He does with us every day.
3)
How will Hashem's Chesed sustain him?
1.
Radak: It will support his heart, lest his legs falter; He will take him out of Galus.
2.
Malbim: It will save him from evildoers.