1)
Why does he request that Hashem destroy his enemies?
1.
Malbim: This corresponds to "teach me to do Your desire" (10). My tormentors are enemies of the Nefesh [who want to make me sin].
2)
Why does it say "Ki Ani Avdecha"?
1.
Radak: They are not Your servants.
2.
Malbim: Therefore, it is proper [that You destroy those who want to make me sin].