1)
Why did he ask her why she hides her identity?
1.
Malbim: You intended that I not prepare myself to have Nevu'ah about Beis Yaravam. This was in vain; even without preparation, I am sent to you with a harsh Nevu'ah!
2)
What is the meaning of "Shalu'ach Elayich"?
1.
Rashi: Hashem gave to me a harsh mission [to tell you].
3)
Why did he say "Kasheh"?
1.
Radak: This is like Chazos Kasheh (a harsh Nevu'ah; the word Chazos is omitted). We similarly find "[u'Ma'achalo] Beri'ah" (Chabakuk 1:16), i.e. Seh Beri'ah (a fat Seh; the word Seh is omitted).
