1)
After he retracts and does evil, will he live?
1.
Radak: No. This is said in astonishment. Malbim - he will die. (a) He abandons the path of Tzedek that he went on, and regrets it. (b) The sins that he does from now and onwards.
2)
Here it says "uv'Shuv Tzadik mi'Tzidkaso v'Asah Avel..." Abaye taught that a Tzadik will not become a Rasha!
1.
Brachos 29a: Our verse discusses one who originally was a Rasha. One who was a Tzadik from the beginning would not sour.
3)
If he was virtuous, and later sinned, he should be considered half-meritorious!
1.
Rashi and Radak citing Kidushin 40b: Our verse discusses one who regrets his merits. He is not rewarded for them.
