What does "v'Avar Bah Niksheh v'Ra'ev" refer to?
Rashi: This refers back to "v'Yisereni mi'Leches b'Derech ha'am ha'Zeh" (11). What is the Derech? "Do not say that the bond [of the 10 tribes to Melech Mitzrayim] is a [proper] bond" (12). It explained the punishment - "v'Hayah l'Mikdash?; v'Chashlu Vam?" (14-15). One who goes on this path, and abandons Hashem and relies on Melech Mitzrayim will be wearied with harsh afflictions and hunger. Sancheriv will besiege Shomron for three years.
Radak: One who will pass in the land mentioned above, i.e. "b'Har Tziyon" (18), will be depressed and hungry; he will not find food. "Niksheh" is [sad,] like "Im Lo Vachisi li'Kshe Yom" (Iyov 30:25).
Malbim: This completes the Nevu'ah of what will be in Efrayim when they are exiled, in Chizkiyah's sixth year. All will be exiled; one who passes through the land will be "Niksheh" - his body was hardened due to all the harsh occurrences. He will be hungry, for the land will be desolate.
Why does it say "Chi Yir'av"?
Radak: He will not know what to do. The hunger is due to war of the enemies.
Whom will he curse?
Rashi: The calves and Ba'alim 1 that they served.
Radak: His king, who has no power to save him, and the idolatry that he served.
Radak citing Targum Yonasan: "B'Malko" is Pesachre; also it refers to idolatry. Also "Sikus Malkechem" (Amos 5:26) 'ha'Nishba'im b'Malkam 2 .'
Malbim: He will curse his day [of birth] in the name of his king and god.
Yaravam set up calves for people to serve in his kingdom, and not go to the Mikdash. 'Ba'al' was the name of a rampant idolatry - "I will leave in Yisrael 7,000 who did not bow to Ba'al? or kiss it" (Melachim I, 19:18). (PF)
Targum Yonasan of that verse is 'Pas Kumarechon' (bread of your priests), close to his translation here 'Pesachre'. Perhaps Radak adds that the preists swear in the name of their idolatry. (PF}
Why does it say "u'Fanah l'Ma'alah"?
Rashi, from Targum Yonasan: He will ask from Hashem. However, He will not heed him, for the decree was sealed.
Malbim (21-22): Wherever he will turn, whether if he faces up, or down, there is affliction.
