1)
What is the meaning of "me'Asher ha'Michmesas"?
1.
Radak: The border went from Asher's border to Michmesas (a place near Shechem). Malbim
2)
Where was Shechem?
1.
Bi'ur ha'Gra: It was an Ir Miklat; it was in the east of Eretz Yisrael. 1
1
The Arei Miklat were chosen to minimize the distance a murderer might need to go to get to an Ir Miklat (Makos 10a). The Gemara asked why murderers near the south and north borders needed to travel further, and answered (there were many murderers in Shechem). If Shechem was in the east, it could have asked why murderers in the west needed to travel further. Perhaps it did not, for clearly the same answer applies. (PF)
