What fire was sent?
Ibn Ezra: "Charon Apo" (23) is compared to fire. It descended from Shamayim and reached my bone.
R. Avigdor citing Eichah Rabah 1:41: It is the fire that burned the Beis ha'Mikdash. Midas ha'Din said, it is not proper that people burn the Heichal; Micha'el and Gavriel set it on fire. The verse laments - had fire not been sent from above, [the enemy] could not have destroyed it.
What is the meaning of "va'Yirdenah"?
Rav Sadya Gaon: He weakened them.
Rashi from Sanhedrin 104b: He broke [my bones] via subjugation and affliction. The Dagesh in the Nun shows that it is singular, like "Ya'asenah" (Mal'achi 2:12), "Yecharsemenah
We find that Rodeh is removing bread stuck to the oven wall! B'Tanur implies that he sticks it. I did not find this in a Mishnah, but it is in Bereishis Rabah 51:2. (PF) Magihah (in Toras Chayim) - Ri Kara holds that the word has both meanings.
What is the significance of spreading a net for the legs?
Ibn Ezra: This is why he cannot flee from the fire.
Ri Kara: These are the enemies that came upon me.
Palgei Mayim: There are two kinds of nets. One is for a damager, to trap it and kill it or make it fall. Sometimes it is to catch [an animal] alive and benefit from it. Hashem spreads a net for Yisrael only in the latter way - "Tashev Enosh Ad Daka va'Tomer Shuvu Vnei Adam" (Tehilim 90:3).
What turned him back [and made him Shomem]?
Ibn Ezra: The fire.
Ri Kara: Hashem turned him back so the enemies caught him.
Palgei Mayim: Hashem's net was only to make me return to Him. Also He made me alone only temporarily - refer to 1:13:5:3.
What is the significance of "Kol ha'Yom Davah"?
Rav Sadya Gaon: Constantly [I mourn]. Ri Kara - Davah is like "v'Chol Levav Davai" (Yeshayah 1:5).
Ibn Ezra: Some Nidos cease [bleeding] at known times, but she [bleeds] the entire day.
Palgei Mayim: I was like a Nidah who is separated from her husband only during her Tum'ah. When she becomes Tahor, she will return to him. So Keneses Yisrael says, Hashem made me alone only when I am filthy with sins. When I will purify myself, He will return me. Davah is like "veha'Davah b'Nidasah" (Vayikra 15:33).