Why does it say "Aram mi'Kedem [u'Flishtim me'Achor]"?
Rashi #1: Aram harmed them earlier 1 , in the days of Yeho'achaz and Yo'ash; Pelishtim harmed them from in back - they are in the west.
Rashi #2: Aram and Pelishtim used to destroy in Yehudah in the days of Achaz, like it says in Divrei ha'Yamim II, Perek 25; Yeshayah laments over these afflictions of Yisrael and Yehudah.
Radak: Before Pekach reigned, Aram fought Yisrael greatly - "va'Ysimam ke'Afar Ladush" (Melachim II, 13:7). Aram was east of Eretz Yisrael.
Malbim: Also Aram itself, which until now helped you, will come against you from the east.
Perhaps Rashi explains that mi'Kedem means before, and also from the east. (PF)
Why does it say "Lo Shav Apo"?
Radak: They did not repent, which would cause Hashem to retract from his anger.
Why does it say "v'Od Yado Netuyah"?
Rashi: [He is still ready to punish] until he will bring Sancheriv against them.
Radak: Hashem's hand is still ready to finish them off, since they did not repent.
