1)
When should Hashem have grace on him?
1.
Rashi: Now, in exile.
2)
Why does he ask Hashem to see his affliction from his haters?
1.
Radak, Malbim: He should do like He did from this hater, i.e. Galyus (Radak; Malbim - Laben).
3)
Why did he say "Meromemi mi'Sha'arei Maves"?
1.
Rashi: Redeem me!
2.
Radak: All thought that I would fall to Galyus. Sha'arei Maves are close to death, just like Beis Sha'ar is close to the house.
3.
Malbim: I was in danger via Laben, one step from death. I was about to enter the gate of death, and You saved me from him.