1)
Why does it say "Gam Atem Gam Malkechem"?
1.
Radak: One in addition to the other (this does not hint to a third matter). This is like "Gam Tzonchem Gam Bekarchem" (Shemos 12:32).
2)
Why did he say "Malkechem"?
1.
Radak: If he does not rebuke you, he will be punished due to you.
