1)
Why does it say both Am Hashem and Beis Yisrael?
1.
Radak #1: They are the same. It is repeated due to the great affliction - Beis Yisrael fell to the sword, and they are Am Hashem!
2.
Radak #2: It says so because most of Yisrael were there. Midrash Shmuel 25:2 says that the verse did not reveal the number, due to "Al Tagidu v'Gas Al Tevasru
