Where in the city should he burn it?
Rashi: In the city that he carved on the brick.
What is the significance of burning a third in the city?
Rashi: This is a sign that a third will die from hunger, which is like fire - "Orenu k'Sanur Nichmaru Mipnei Zal'afos Ra'av" (Eichah 5:10).
Radak, Malbim: This is a Mashal for those who will die in the city, from hunger and plague, from the siege until it is captured.
What do we learn from "Takeh va'Cherev Sevivoseha"?
Rashi: It is around the brick. This is a sign that those who flee the city (Radak - Tzidkiyah and his entourage), the Kasdim will catch them and kill them around Yerushalayim (Radak - in Arvus Yericho).
Malbim: This refers to the enemy striking with the sword around the city.
What is the significance of casting a third to the wind?
Rashi: This is a sign of those who will go to exile in Egypt - Yochanan ben Kare'ach and his group. I will send my sword after them - Nebuchadnetzar went and destroyed Egypt, and there they were killed.
Radak: Dividing the hair in three parts is a Mashal for Yisrael, who are shaven and removed from their land and from the world - some via hunger and some via Galus.
What is the significance of "Arik Charbi Achareihem"?
Rashi: Nebuchadnetzar went and destroyed Egypt, and those who went there were killed. Radak - the Navi told them, the sword that you fear [and flee from], it will catch you in Egypt. They went also in other lands before the Churban, like it says in the episode of Gedalyah. Harakah of the sword is removing it from its case. Also in the Tochachah it says "va'Harikosi Achareichem Cherev" (Vayikra 26:33).
Malbim: This refers to those who fled the enemy and scattered in every direction. The sword will catch many of them in their enemies' lands.