Why does it say "Sim Lecha Shenayim Derachim"?
Rashi: This is like the verse concludes.
Radak #1: Think in your heart that there will be two paths.
Radak #2: Prepare two paths. This is like "Kach Lecha Levenah" (4:1). All this was in a prophetic vision.
Malbim (23): You should depict two distinct paths prepared for Melech Bavel's sword to go there.
Why does it say "Lavo Cherev Melech Bavel"?
Radak: His sword will go on one of the paths. This is the sword that I took out of its scabbard and sharpened and polished it, and gave it in the hand of the killer, i.e. Melech Bavel.
What do we learn from "me'Eretz Echad Yatz'u Sheneihem"?
Radak citing Targum Yonasan: Both paths came from one land. Radak - i.e. Bavel. Here, Eretz is masculine (it says Echad), like "v'Lo Nasa Osam ha'Aretz" (Bereishis 13:6)
What is the meaning of "v'Yad Barei b'Rosh Derech Ir Barei"?
Rashi: Clear for yourself room at the head of the path that you are on. Make for yourself like a crossroads ? one turns to the left, and one to the right. Yad 1 Barei is a place clear from thorns. This is like "Ale Lecha ha'Yarah u'Verasa Lecha Sham" (Yehoshua 17:16).
Rashi citing Menachem: Barei is an expression of Bereirah (selecting), like "Beru Lachem Ish" (Shmuel I, 17:8). Radak ? both of these are commands, just the last letter of the root of Beru is Hei, and the last letter of the root of Barei is Aleph; it is like "u'Verasa Lecha Sham." Choose a place that both paths turn to there. So Melech Bavel will do - he will stand at the crossroads to see which way he should go. You should choose this place at the head of the entrance to the city.
Malbim: There should be an empty place at the end of each path. At the head of each path he should clear one city and cut it off, to be an empty place for Nebuchadnetzar's camp. This is a sign that wherever he will go, on one of the two paths, he will cut off and clear the city, and make a place for his camp.
Radak: Yad is a place, like "v'Yad Tihyeh Lecha mi'Chutz la'Machaneh" (Devarim 23:13).