1)
Why does it say Oyvi (singular)?
1.
Radak: This refers to Galyus, or Yishbi b'Nov, or perhaps Sha'ul.
2)
What is the difference between an Oyev and a Sonei?
1.
Malbim (Tehilim 18:17): A Sonei hates, but does not seek to harm. An Oyev hates and seeks to harm.
3)
What is the meaning of "Ki Amtzu"?
1.
Rashi: It is when [they were stronger than me].
