Who are "Somechei Egypt"?
Radak: They are Bnei Eretz ha'Bris and the other nations mentioned, who supported and helped Egypt.
Malbim: There are the many nations who help it. They are one of the four sources of Egypt's power; all of them will perish. The others are (a) the multitudes who lived in Egypt, (b) the rivers, and (c) they believed that all of them came from gods, and their king at the head.
Why does it specify "mi'Migdol Sevenah"?
Radak: This is the border of Egypt on one side. The sword will begin to consume them from there, until the border of Kush, like it said above "mi'Migdol Sevenah v'Ad Gevul Kush" (29:10). The verse did not mention Kush here, for it already said above that it is the other border.
What does "Vah" refer to?
Radak: It refers to Eretz Egypt.
