What is the net?
Radak: Sha'ul told the Zifim "u'R'u Es Mekomo Asher Tihyeh Raglo" (Shmuel I, 23:22).
Malbim: It is a net to [trap and] kill me. Since I am in the ultimate danger, hear my Tefilah and reverse [the net] on them! They reached the cave where David and his men were.
What is the meaning of "Kafaf Nafshi"?
Rashi: The enemy bent [my Nefesh]. This is like "v'Zokef l'Chol ha'Kefufim" (145:1).
Radak #1: Sha'ul bent and humbled my Nefesh.
Radak #2: "Kafaf" is Po'el Omed (the action applies only to the subject). They set a net for my steps, to the point that my Nefesh bent. Here, Nefesh is masculine, like "Echad Nefesh" (Bamidbar 31:28).
What is "Shichah"?
Radak: It is like Shuchah with a Shuruk, "Shuchah Amukah" (Mishlei 22:14; a pit). Malbim - people who hunt Chayos, they dig a pit for the Chayah to fall into after it is caught in the net.
Did they already fall in the pit?
Rashi: In the end, they will fall in it. Radak - most Nevu'os use past tense in place of future.
Malbim: I was prepared to fall in it - however, I did not fall in it, rather, they did.