1)
What are "Avos"?
1.
Radak: They are ropes of the yoke.
2)
Why does it say "Hashem Tzadik Kitzatz Avos [Resha'im]"?
1.
Radak: Past tense used in place of future. Hashem who is Tzadik and straight in His ways, will cut the ropes of the yoke, i.e. remove their yoke from on us.
2.
Malbim: He cut the ropes of the yoke, to the point that the cattle could not conduct the plow tools. It was not due to the land being plowed; rather, Hashem annulled the counsel of those who plow, and cut our ropes.
