What is "Mekunant ba'Arazim"?
Rashi: You put your nest in towers, houses of cedar, of great measure.
Malbim: Animals that give birth to live babies and nurse them, they have Chen on (pamper) them at the time of birth, since the birth is difficult. Ewes may not go out Chanunos. I.e. when it gives birth, they put on it tufts soaked in oil
What is the grammatical form of "Yoshavt" and "Mekunant"?
Radak: Each of them is composed of two words - Yashavt and Yosheves, and Mekanant and Mekonenes 1 . Both are written with a Yud at the end, but it is not pronounced. Sometimes the extra Yud is pronounced - "Ohavti Ladush" (Hoshe'a 10:11), "Mela'asi Mishpat" (Yeshayah 1:21).
Radak: This hints that these actions were from before, and also now. They were still in the land attributed to Levanon. It mentions Levanon and cedars because there were big buildings in Yerushalayim covered with cedars, e.g. Beis ha'Melech, like it says about Yehoyakim "v'Safun ba'Erez" (verse 14).
What is the meaning of "Mah Nachanta"?
Rashi: What Chen (grace) did you find due to the height of your towers in the eyes of your plunderers when birth pangs came on you? Also Dunash said that Nachanta it is an expression of Chen.
Rashi citing Menachem: Nachanta is an expression of Chaniyah (camping).
Radak: "Mah" can be due to an attribute - "Mah Rav Tuvcha", "Mah Yekar Chasdecha Elokim" (Tehilim 31:20, 36:8), or a shortcoming - "Mah Enosh Ki Sizkerenu" (ibid., 8:5). Here it can be an attribute - what grace and beauty you had when the birth pangs and afflictions came on you!
Radak #2: Here, "Mah" is a shortcoming - what grace remained to you from all that you built, when the birth pangs and afflictions came on you?
Malbim: What pampering did they do for you when the birth pangs came on you? This is a metaphor for the exile of Yehoyachin, his mother and servants - "va'Yegel Es Yehoyachin Bavelah v'Es Em ha'Melech v'Es Neshei ha'Melech