1)
Why did he say "Yad Hashem"?
1.
Malbim: Do not say that He will merely remove His Hashgachah. (Rather, Hashgachah will punish you.)
2)
What is the meaning of "uva'Avoseichem"?
1.
Rashi, Targum Yonasan: [Hashem's hand] will be against you, like it was against your fathers [when they rebelled against him - Malbim].
2.
Rashi (citing Yevamos 63b): This is an affliction that people will dig and remove the dead from their graves. It is disgrace to the dead.
3.
Radak (14): It is your king. A master to his nation is like a father to his son - "va'Ysameni l'Av l'Pharaoh" (Bereishis 45:8).
