1)
Why is "Kav" written with a Hei at the end?
1.
Radak: We find this name in the female, e.g. "Tikvas Chut ha'Shani" (Yehoshua 2:18). It is pronounced Kav (masculine), like the majority.
2)
What are "Garev" and "Go'asah"?
1.
Radak: They are names of places. They were known to them in Yerushalayim, or nearby.