1)
What is the meaning of "Tzedek Edvosecha l'Olam"?
1.
Malbim: The Edos that the Torah testified via its tales, that You release Tzadikim from their affliction, is always Tzedek and conducts always.
2)
To what does "v'Echyeh" refer?
1.
Radak: I will live forever, in the world to come. "L'Olam" refers also to "v'Echyeh".
2.
Malbim: I request that You make me understand these Edos, so I will understand how You punish Resha'im and save Tzadikim. Often there are perplexities in hidden matters of this conduct, for people see Resha'im succeeding and Tzadikim afflicted.