1)
Who was the Mal'ach?
1.
Rashi (like R. Pinchas, in Shochar Tov 18): It was an angel. Radak - "Yishlach mi'Shamayim v'Yoshi'eni" (Tehilim 57:4).
2.
Radak (like R. Yudan, in Shochar Tov 18): It was a Shali'ach 1 [Malbim - through Hashgachah Pratis].
1
Radak: R. Pinchas rejected this, for a Shali'ach would not counsel Sha'ul "Meherah v'Lechah."