1)
Why does it say "Lishmo'a Al ha'Nevi'im"?
1.
Radak: Al is like El. Also "va'Yelech Elkanah ha'Ramasah Al Beiso" (Shmuel I, 2:11) is like El Beiso, and similar verses.
2)
Is "Lishmo'a Al ha'Nevi'im" the Perush of "Laleches b'Sorasi" (verse 4)?
1.
Malbim (4): No. You must heed Torah and Divrei ha'Nevi'im, and then the Bayis will not be destroyed.