1)
The first time, Hashem said "Rav ha'Am Asher Itcha" (verse 2). Why did He omit "Itcha" now?
1.
Malbim: The first ones who left were not idolaters; they resembled Gid'on. The ones who would leave now were idolaters; they did not resemble Gid'on.
2)
What is the meaning of "v'Etzrefenu Lecha Sham"?
1.
Radak: This is like one who is Metzaref silver (removes its impurities). Only Tzadikim will be in the war.
3)
Why is there the repetition "Yelech Itach... Yelech Itach... Lo Yelech Imach... Lo Yelech"?