1)
Why does it say "Mi Zeh ha'Ish Yere Hashem"?
1.
Radak: One who wants to fear Hashem should prepare his heart.
2.
Malbim: After asking Hashem to grace him with all his physical and spiritual needs, he says that for true Yir'ei Hashem, there is a better path than what he prayed for until now - to totally despise worldly matters.
2)
What is the meaning of "ba'Derech Yivchar"?
1.
Rashi: Hashem will lead him in the path that He 1 chose - the good path.
2.
Radak: Hashem will help him and show to him the path that Hashem chooses that man go on - the good path.
3.
Radak citing Ibn Ezra: Man will choose the path.
