1
ואתה, מגן - שם ואינו פועל כי היה ראוי להיותו על משקל הנני מסב. But You, [Ad-nai], a shield (מָגֵן - magen): [This word magen] is a noun (shem) and not a participle (po'el). For [if it were an active participle meaning "shielding"] it would properly be in the pattern of [a form like] Hineni mesev ("Behold, I am surrounding/shielding").
2
וטעם מגן – שהוא לא בא במלחמה. And the meaning of shield is that he [David] did not [need to] enter into battle [because God protected him].
3
וטעם כבודי – כי כל המנצח יש לו כבוד. And the meaning of my glory (kevodi) is because everyone who is victorious (ha-menatzeach) has glory/honor. [God is the source of his victory and thus his glory].