1)
Why did he say "Ki Sa'aneni Kel"?
1.
Rashi: I am sure that You will answer me.
2.
Radak, Malbim: I called to You because I trusted that You will answer me and You can help me. Malbim - after David clarified his virtue, he begins to complain about his enemies' pursuit of him.
2)
Why did he add "Hat Aznecha Li Shma Imrasi"?
1.
Malbim: This is a lover's way - not only does he fulfill the request. He also hears all the details that his beloved says.