Why does it mention his eyes and heart?
Malbim: These are two brokers of sin (Yerushalmi Brachos 1:5).
What is "Bitz'echa"?
Rashi: It is stealing money.
Radak: It is your desire for money.
Malbim: It is your benefit. You act and think only for this, and not for the good of the Klal!
Why does it mention spilling innocent blood?
Malbim: A king needs to supervise that people not murder, and punish murderers. You supervise only on innocent blood, ton spill it!
What is "ha'Merutzah"?
Rashi: It is crushing the poor and withholding what is his. We always find them together 1 - "v'Es Mi Ashakti v'Es Mi Ratzosi" (Shmuel I, 12:3).
Radak: It is breakage - "v'Es Mi Ashakti v'Es Mi Ratzosi" (Shmuel I, 12:3). Even though it is not from the root, we find like this when the middle letter of the root is silent, e.g. "Lo Yichheh v'Lo Yarutz" (Yeshayah 42:4). Oshek is monetary, and Merutzah is bodily. He used to be Oshek (withhold) wages, like it says, and beat them and force them to word for him; this is Merutzah. It says about these, and murder, "v'So'avosav Asher Asah veha'Nimtza Alav" (Divrei ha'Yamim II, 36:8), and on this Sefer, which discusses Yisrael, Yehudah and their kings 2 .
Perhaps he means that we often find them together. We find each without the other, e.g. "Gazul mi'Yad Ashok" (verse 3), "Lo Yichheh v'Lo Yarutz" (Yeshayah 42:4; Rashi himself says that it is an expression of Ritztutz! (PF)
This Sefer mentions Malchei Yisrael only incidentally! This requires investigation. (PF)
Why does it say "La'asos"?
Malbim: You do not supervise Oshek and Merutzah to stop them, rather, to do them!