Who was this Navi?
Rashi, Targum Yonasan: It was a Navi Sheker.
Radak citing Yerushalmi Brachos 9:2: It was Michah.
Radak citing Shir ha'Shirim Rabah 2:5 #1: It was Amatziyah Kohen Beis Kel.
Radak: Some say that it was Ido 1 ha'Navi.
Radak citing Shir ha'Shirim Rabah 2:5 #2: It was Yonason ben Gershom.
I did not find such a source. Radak brought it between opinions in Shir ha'Shirim Rabah; perhaps it was in his text there. This is unlike Sanhedrin 89b, which says that Ido rebuked Yaravam. (PF)
Why does it say "Yoshev b'Beis Kel"?
Rashi: He was not from there; he came from Shomron, like it says [when Yoshiyah burned the Kohanim's bones] (Melachim II, 23:18) "va'Ymaltu Atzmosav Es Atzmos ha'Navi Asher Ba mi'Shomron." Radak - even though Shomron was not built at that time - Amri built it later (16:24) initially it was an open city. Amri acquired the mountain, and built the city. Or, there was a [walled] city there initially, like Targum Yonasan there (u'Zvan Yas Keracha); Amri strengthened the Binyan (wall) and called it a new name.
What are "ha'Devarim Asher Diber"?
Malbim: The Nevu'ah for the future about the Mizbe'ach, and Hashem's command that he not return the same way [or eat].
Before it said that his son told him. Why does it say now "va'Ysaprum"?
Radak, Malbim: Initially one son came and told him what Ish ha'Elokim did. While he was telling him, his other sons came and told their father like the first son told him.
