1)
What is "Maginenu"?
1.
Rashi: It is the Beis ha'Mikdash, which shields us.
2.
Radak: You, Hashem, who shield us.
2)
What is the request "v'Habet Pnei Mashichecha"?
1.
Rashi: Look at his Chasadim, and his toil to build the Beis ha'Mikdash.
2.
Radak #1: Bring Mashi'ach soon in our days. Habatah of the Panim is Hashgachah over man and desire.
3.
Radak #2: If the Mizmor discusses David, it refers to David.
4.
Malbim: It is Malchus Beis David. It and the Beis ha'Mikdash (Maginenu) depend on each other.