Once that impetus is set (and in God’s case would certainly be fixed - “the always good”), the rest of the decision making process is already determined because there is only one “good”.
Everyone’s will is set to the “always good”; the difference between us and God is that our knowledge is faulty and our power is weak. We still will the “always good”, we just don’t know exactly what it is (or which factors will lead to it), nor do we always have the power to fully enact it.
There is not a single being in the universe who’s will is not set to the “always good”, not even Satan.
This is to say that God cannot make a choice to do the bad simply because of his own unchangeable sense of good. This means that he is predictable to anyone who also knows that good because God will always do that same thing in that same circumstance. That is what makes Science and logic actually work (when they don’t screw it up).
Nobody can make the choice to “do bad”. You’re thinking of “good” only in the moral sense, and not in the full sense of the word. The will is, by necessity, aimed towards the good. If I choose to murder, I may be falling short of the absolute good, but my will is aiming at the good (namely the good of my needs being met, whatever they may be). It is utterly impossible to “will the bad/evil” by definition.
A moral man can be in the same situation. If a man gains, by whatever means, a sense of right and wrong and also a strong will to always do the right, then he has no choice other than to do the right. His own desire forbids him from deciding otherwise. If someone removed his sense of right and wrong or removed his desire to do right, then he might become unpredictable and actually free to go either way because he would be free from the sense of guilt or from the awareness of right and wrong (insanity - typical American).
If someone removed his absolute sense of good and evil, he would still be seeking the good, but his “guidance system” would be shorted out. He would be like a blind, senseless mouse in the afforementioned maze. He may now make all kinds of choices, but his will is actually LESS free to seek the good because it is more inhibited from its natural inclination. It still seeks the good, but it has less sense of proportion, less sense of what choices lead to the ultimate good. He is stuck with a poor measuring system, and so is left grasping for any possible good that comes along, regardless of relative worth and ultimate satisfaction of the will.
Unpredictability is not freedom, certainly not for something made for a certain end (as the will is made for the good). You are not freer to travel in a vehicle that turns in random directions, and you are not freer without a sure roadmap, but rather you are lost and hopeless. The broken man that you describe might make any choice, but he would have a much harder time making the choice that best serves his will, just as the broken car can move forward in any direction at any time, but it won’t get you where you want to go.
God, not being one who can be altered such as to remove his sense of right and wrong, nor remove his will to do right, cannot actually do anything but the right - ever. **= **one and only one choice and absolutely no freedom from his own sense of right and wrong nor from his desire to do the right.
You’re still mistaking the failure of the will to fulfill itself as freedom. The will seeks the good, period. God can not do other than seek the good, and neither can we, but God has the unfettered power to hold the ultimate good, whereas we do not. We stumble and often make choices for the good that hinder us from the ultimate good, the ultimate thing our will seeks. We have a blindfold, and though our will seeks the good by necessity, we stumble in the darkness grasping at the faintest glimmers of it, rather than walking directly towards it.
The sense of right and wrong is not a constraint, it’s a fulfillment and a perfection. The lack of this sense is the constraint, just as losing the sense of sight is a constraint on moving in the proper direction. You are still substituting a straightjacket for freedom, and calling it freedom because now you have so many options for trying to escape it.
Peace and God bless!