1)
Why does it say "v'Hinei"?
1.
Malbim: Via Hashgachah, he came when Yaravam was on the Mizbe'ach to offer Ketores. Had he come earlier, they would not have let him come to the Mizbe'ach.
2)
Who was the Ish Elokim?
1.
Rashi (from Sanhedrin 89b): It was Ido. Radak - Divrei ha'Yamim II, 9:29 supports this - "uva'Chazos Yedo 1 ha'Chozeh Al Yaravam."
1
Even though there it says Yedo, it seems that this is Ido, who is called Chozeh, and prophesized about Rechav'am (Divrei ha'Yamim II, 12:15). However, one opinion says that Ido is the Navi who invited this Navi to eat (refer to 13:11:1:4)! (PF)
