1)
What is the meaning of "Dibarti Mishpat Osam"?
1.
Rashi: I will dispute with them - with Yehudah and Yerushalayim.
2.
Radak: My talk with them brought the kings against them. This is like Elihu said [to Iyov] "Ki v'Achas Yedaber Kel uvi'Shetayim Lo Yeshurenah; uv'Mosarim Yachtom" (Iyov 33:14, 16). The Dibur was that He will bring punishments on them to rebuke them.
3.
Malbim: I will arrange my case and claims in front of these judges, to request judgment from them.
2)
Why did He say "Asher Azavuni"?
1.
Malbim: Their evil was three-fold. (a) They abandoned Me. (b) They served other gods. (c) They bowed to the work of their hands (they know that it does not help)!