1)
Why is this paying bad for good?
1.
Radak: I spoke good about them in front of You, and I prayed for them until You told me that they want to kill me.
2.
Malbim: All my Nevu'ah for them was for their good, so they would repent and annul the decree. I always stood in front of You to pray for them to repel anger.
2)
What is the meaning of "Charu Shuchah l'Nafshi"?
1.
Radak: They wanted to give to him poison to drink, like they dig a pit for a man to make him fall in unaware.