1)
What is "Peger"?
1.
Metzudas David: It is a corpse.
2)
Why was David confident that all the Pelishtim will be defeated today?
1.
Malbim: Hashem will hand them over to one man who trusts in Hashem.
3)
To whom does "Kol ha'Aretz" refer?
1.
Malbim: It is the nations who do not believe in Hashgachas Hashem. They will recognize that there is Elokim for Yisrael!