1)
Whom does the verse address?
1.
Rashi: It addresses Yisrael [Radak - in Galus Bavel].
2)
What are "Atzbecha" and "Ragzecha"?
1.
Rashi: Melech Bavel saddened and agitated you. When you see his downfall, [Hashem] will relieve you, for you will go free.
2.
Radak: "Atzbecha" is the pain of Galus.
3.
Malbim (Bi'ur ha'Milos): Otzev is pain over something lost and missing. Rogez is due to evil occurring to him now.
3)
Why does it say "Ubad" (masculine)? "Avodah" is feminine!
1.
Radak: It refers to the Inyan (matter) of Avodah. Similarly, "Ye'aseh Melachah" (Shemos 31:15) and similar verses.