1)
What is the meaning of "v'Sa'ar ha'Gevul"?
1.
Malbim: It surrounded the mountain on three sides.
2)
What is the meaning of "v'Nasav li'F'as Yam Negbah"?
1.
Rashi: [Atros Adar was the northwest corner of the border. From there] it turned to the south.
3)
Where was Kiryas Ye'arim?
1.
Malbim (19:1): It is half the length of Eretz Yisrael [from east to west].