1)
Why are there so many repetitions of help and salvation of Tzadikim, and punishment of Resha'im?
1.
Radak: The repetition shows the great help and salvation. The Resha'im's punishment is repeated to teach that their success will not endure. Most people are enticed to desire the Resha'im's success and do like them, so the Mizmor repeatedly warns against this.
2.
Malbim: He spares Tzadikim from Resha'im, and saves them so Resha'im cannot harm them.
