What is the meaning of "Niskad"?
Rav Sadya Gaon: He held and tied my sins in His hand.
Rashi: There is nothing like this word in Tanach. In Pesikta, in Arame'ic, Darban (a plowshare) is called Miskada. I say that it is dotted and marked 1 . So Yisrael's sins 2 were remembered in Hashem's hand, lest their number or payment be forgotten.
Ri Kara: [My sins were] written and sealed [in His hand]. "Ol" is like "v'Olasah Kaftzah Fiha" (Iyov 5:16).
Rid: My sin is seen [in His hand].
R. Avigdor: Niskad is like Shakad. Hashem was merciful [and considered how to exile them in the best way]. If I will exile them in spring, "Ein Anavim ba'Gefen v'Ein Te'enim ba'Te'enah
What is "Yistargu"?
Rashi: [The sins] were braided. This is like a Mishnah (Mo'ed Katan 8b) 'Mesargin Es ha'Mitos.'
Ibn Ezra: This is Hispa'el; it is like Sarigim (Bereishis 40:10). The nature of vine branches is to hold (wrap around) any high tree [nearby].
Ri Kara: The sins grew and became branches.
Rid: They grew and became thick.
What sapped his strength?
Ibn Ezra: "Ol Pesha'ai."
R. Avigdor citing Eichah Rabah 1:43: There are five things that weaken a person - sin ("Hichshil Kochi"), traveling ("Inah va'Derech Kochi" - Tehilim 102:24), fasting ("Ineisi va'Tzom Nafshi" (ibid., 35:13), kingship ("Alu Al Tzavari Hichshil Kochi") and hunger {"bi'Ydei Lo Uchal Kum.")
How did Hashem give him?
Ibn Ezra: He abandoned him to [suffer the results of] his sins, or to the enemy. This is like "Al Ken Lo Nesaticha" (Bereishis 20:6).
Palgei Mayim: (He gave him to the enemy for a small punishment, but the enemy added.) This is like "Ani Katzafti Me'at v'Hemah Azru l'Ra'ah" (Zecharyah 1:15). How can they add to the decree of the One who said, and the world came into existence?! Rather, they cause us to sin; via this, they add to the evil. Hashem weakened us via putting me in the hand of nations that make us sin so we cannot stand (refer to 1:14:5:4).
In what way can he not stand?
Rav Sadya Gaon: He cannot oppose [his enemies].
Ibn Ezra: He cannot stand due to his sins.
Rid: He cannot leave Galus. Yisrael left Galus Bavel after 70 years! Rather, Yirmeyah saw [with Ru'ach ha'Kodesh] both Churbanos. Eichah is primarily about our Galus (via Edom).
Palgei Mayim: He cannot justify his deeds and return to Hashem.