1)
Why did he say "Kulchem Bnei Yisrael"?
1.
Radak: He called to them.
2.
Kli Yakar (Lani'ado): He addressed also Binyamin.
2)
What are "Davar" and "Etzah"?
1.
Malbim: Davar is the verdict what to do. Etzah is how to carry it out to eradicate the sinners.