1)
What is the request "Hafked Alav Ra'ah"?
1.
Radak: A Rasha should rule over them.
2.
Malbim: They say to appoint an evil judge over me to judge me.
2)
What is the meaning of "v'Satan Ya'amod Al Yemino"?
1.
Radak: A prosecuting angel should stand at his right hand to oppose him. I.e. everything he does should be a curse. The singular is used for the head of the Resha'im who hate him, i.e. Do'eg ha'Edomi.
2.
Malbim: A prosecutor should stand at the right of the judge (refer to 109:6:1:2) at the time of the judgment.