1)
Why does it say "Za'akti" and "Amarti"?
1.
Malbim: These correspond to "Koli El Hashem Ez'ak" and "Koli El Hashem Eschanan", respectively. Here it explains the supplication - a free gift not due to merit.
2)
Why did he say "Atah Machsi"?
1.
Malbim: This is one reason for You to help me. You are always my shelter - You do not change! Also refer to 142:6:3:3.
3)
What is the meaning of "Chelki b'Eretz ha'Chayim"?
1.
Radak: Again [in the future] my portion will be in Eretz Yisrael. I explained above why it is called Eretz ha'Chayim (refer to 116:9:3:2).
2.
Malbim: This is the second reason for You to help me. Since You gave my portion in life, it is proper that You guard my life.
