What is the meaning of "Afafuni"?
Rashi: I am surrounded. Malbim (Tehilim 18:5) - death is on one side, and enemies on the other side.
What are "Mishberei Maves"?
Rashi citing Targum Yonasan 1 : It is like a woman sitting on the Mashber (stone on which women give birth).
Radak #1: They are great afflictions close to death, e.g. at Sela ha'Machlekos (Shmuel I, 23:28). They are Shover (break) the heart via his worries.
Radak #2: It is a metaphor, as if it says waves of death. Strong waves are called Mashberim - "Kol Mishbarecha v'Galecha Alai Avru" (Tehilim 42:8). A wave is called so because it is broken through its strong movement.
The Targum adds 'she does not have strength to give birth, and she is in danger.'
What are "Nachalei Veliya'al"?
Rashi: They are troops [of Resha'im] who flood like a river.
Radak #1: This is a metaphor. Like a flooding river, so is a great affliction.
Radak #2: This is an expression of illness, like "Nachlah Makasecha" (Nachum 3:19, Yirmeyah 30:12).
What is "Veliya'al"?
Radak #1: Every Rasha of his enemies is called Beliya'al.
Radak #2: Beliya'al is the name of the Rasha.
Radak citing Targum Yonasan: A company of Resha'im.