1)
Why does he request to live?
1.
Radak: I request in this world, in order that I will know the truth of Your Elokus. This is the praise that I will give to You!
2.
Malbim: I request in order to praise You, for "Lo ha'Mesim Yehalelu Kah" (115:17).
2)
How will the Mishpatim help him?
1.
Radak: They are like a ladder to ascend to knowing Elokim.