1)
What is the meaning of "Tzedek Lefanav Yehalech"?
1.
Radak: Tzedek will go in front of a man, i.e. it will always be in front of his face.
2.
Malbim: The verse depicts that Hashem's Tov does not want to go on the road alone, until a guide will go in front of it - Tzedek.
2)
What is the meaning of "v'Yasem l'Derech Pe'amav"?
1.
Rashi: Hashem will make Tzedek the path of His steps; He will conduct His children with it.
2.
Radak: He will put his steps on the path of Tzedek. The matter is repeated [in different words] to strengthen it.
3.
Malbim: The verse depicts that only after Tzedek will go in front of it, then Tov will go in back of it.