1)
What is the meaning of "u'Mah Yosif David Od Ledaber Elecha"?
1.
Rashi: What else will I ask?
2.
Malbim: If I will ask why You chose me and my house [this only You, with Your all encompassing knowledge, can know].
2)
What is the meaning of "v'Atah Yadata Es Avdecha"?
1.
Rashi: You gave to me all my needs. This is like "Yode'a Tzadik Nefesh Behemto" (Mishlei 12:10).
2.
Radak: You know what is in my heart. I do not know [how] to speak what is in my heart, and You know!
3.
Radak citing Targum Yonasan: You did the request of Your slave. This is like "Mah Adam va'Teda'ehu" (Tehilim 144:3).
4.
Malbim: Refer to 7:20:1:2.