1)
Why did they say "k'Vo'achen Tavo'u El Am Betach"?
1.
Malbim: If k'Vo'achen (you go immediately), they will not fight at all. If you delay, perhaps they will find out [your plans] and prepare themselves for war.
2)
What is the meaning of "Kol Davar Asher ba'Aretz"?
1.
Radak: Whatever is in this land, or any land in the world [you will find there. It is not lacking anything.]
2.
Malbim: Whatever is found in Eretz Yisrael [is there].