1)
What is "ha'Har he'Chalak"?
1.
Rashi: It is the smooth, slippery mountain. 1 Until Ba'al Gad is in the eastern border. 2 Yehoshua did not suffice in his lifetime to conquer the entire border until the north (Tosefta).
2.
Radak, citing Targum Yonasan: It is the divided mountain. I.e. part is here and part is there.
1
Radak: This is like "Anochi Ish Chalak" (Bereishis 27:11). It did not have trees.
2
Perhaps this is a second Perush, like Targum Yonasan and Radak
2)
What is "Ba'al Gad"?
1.
Rashi citing Targum Yonasan: It is the plain of Gad. 1
1
Rashi (Bereishis 14:6): The name of the plain is Gad. Rashi (Shir ha'Shirim 8:11)