1)
Why does it say "va'Ychal ba'Hevel"?
1.
Radak: Hashem told them "Tis'u Avonoseichem Arba'im Shanah" (Bamidbar 14:34). They died every year, until everyone above 20 died.
2.
Malbim: "Beneichem Yihyu Ro'im ba'Midbar Arba'im Shanah v'Nas'u Es Zenuseichem" (Bamidbar 14:33).
2)
Why does it say "ba'Behalah" with a Patach under the first Beis?
1.
Radak: This refers to the known Behalah, from which the Meraglim died suddenly in a plague.
