1)
What is "l'Es Ziknah"?
1.
Rashi: If I became old in sins, i.e. I sinned much.
2.
Radak: Now that I am old and weak. Malbim - if You will abandon me now, people will say that what I did until now was due to my great strength, and now that my natural strength faded, my Gevurah ceased.
2)
What is the meaning of "Al Ta'azveni"?
1.
Radak: Be my strength and fortress.