1)
How is the Ketz on you?
1.
Radak: The verse addresses Eretz Yisrael; the four corners of the world are on it.
2)
What is the significance of sending His anger on you?
1.
Malbim: This is not natural, rather, via Hashgachah of His anger.
3)
Why does it say "u'Shfateticha"?
1.
Malbim: I will punish you from two aspects. (a) I will look at the Nefesh of the sinner ? if the sins became rooted in the Midos and natures of the Nefesh, and his thoughts are full of plans to sin, and they are not occurrences based on a desire at the time. This is punishment "ki'Drachayich". (b) Based on the quantity of sins ? "Kol To'avosayich."