What comes to my mind is Adam and Eve. I see them in a similar test (with devastating consequences) one to resist temptation. They, however, had unadulterated spirits, as well as the advantage of a perfect environment. What allowed them to sin was their free will. I assume that Job had the capacity to sin in his situation, on account of his free will. Our free will is what is so foundational, right? So I think free will allows the idea that Job could have sinned to be entertained.
You are absolutely correct. The first humans had no sinful nature, so there was no "mistake" made....what they both did was willful and deliberate. They knew the consequences before they acted, but can you see the trap that the devil set for them? Each one of them ate the fruit...but for a different reason.
Do you know why the devil was even there in the garden?
We find the answer in the book of Job.....in addressing the King of Tyre, God said....
"In Eʹden, the garden of God, you proved to be. Every precious stone was your covering, ruby, topaz and jasper; chrysʹo·lite, onyx and jade; sapphire, turquoise and emerald; and of gold was the workmanship of your settings and your sockets in you. In the day of your being created they were made ready. 14 You are the anointed cherub that is covering, and I have set you. On the holy mountain of God you proved to be. In the midst of fiery stones you walked about. 15 You were faultless in your ways from the day of your being created until unrighteousness was found in you.
Because of the abundance of your sales goods they filled the midst of you with violence, and you began to sin. And I shall put you as profane out of the mountain of God, and I shall destroy you, O cherub that is covering, from the midst of the fiery stones.
17 “‘“Your heart became haughty because of your beauty. You brought your wisdom to ruin on account of your beaming splendor...." (Job 28:13-17)
This was a clear description of the devil, whom the King of Tyre, by his conduct, emulated.
Satan was right there in the garden of Eden as an anointed cherub....a high station among the angels in a guardianship capacity. According to this description, he was a very beautiful creature who got carried away by his own magnificence. He was at first perfect...until he entertained some very wrong ideas....but rather than dismissing them, he plotted a way to separate the humans from God and to lure them away to a course of rebellion so that he could claim them as his own worshippers.....this was an abuse of
his free will.
He had observed that the man had spent a long time waiting for God to bring him a mate.....so when she finally arrived, he was besotted. She was the "newby" and God appointed her husband as her instructor. God had educated the man....now he would educate his wife and together they would educate their future children.
When the devil offered his temptation, she well knew the most important thing was not to even touch the TKGE, or else they would die....she told that to the devil, who masqueraded as a serpent so as not to give himself away.
Whether he used a serpent like a ventriloquist, or simply materialized a serpent's body, we do not know, but it worked, and that was all that mattered to him. The woman was not blamed for sin entering the world, it was the man who sealed the fate of humanity. (Romans 5:12)
Satan targeted the woman to get to the man. The Bible says that she was thoroughly deceived by satan's ploy and ate, genuinely believing that her good life could be even better with this added bit of knowledge that he convinced her would be beneficial.....when death did not come immediately, it probably seemed to her that God was not telling the truth, so she offered some of the fruit to Adam.....when she offered it, Adam was faced with a dilemma.....his loyalties were immediately divided and he knew that she would die because she had disobeyed God's command....but he had opportunity to decline her offer as a test of his loyalty, and save the human race.....but he chose instead to join her, and thus sentence all of their future children to the same fate....enslavement to sin and death. God has been steadily undoing all the damage ever since and choosing the citizens of his Kingdom in the process.
However, there’s the problem that God can’t be wrong. So if He said Job would hold up, at that point did Job lose his freewill in the matter? Is it simply a consequence of omniscience?
God is all knowing and if he chooses, he can know exactly what will happen in the future...he would not be able to author prophesy unless he had this ability.
Isaiah 46:9-11....
"Remember the former things of long ago,
That I am God, and there is no other.
I am God, and there is no one like me.
10 From the beginning I foretell the outcome,
And from long ago the things that have not yet been done.
I say, ‘My decision will stand,
And I will do whatever I please.. . . .
I have spoken, and I will bring it about.
I have purposed it, and I will also carry it out."
God's ability to see the future allows him to make decisions ahead of time....this way he knows how things will turn out....but he does not alter the outcome.....that is for his free will creation to decide.
In the case of Adam and his wife...there were several outcomes that could have been decided.....
1) The devil could, of his own free will, have restrained himself from stepping out of line, preventing what followed.
2) He could have offered the fruit to Eve and she could have declined after having quoted God's command.
3) Eve's offer to Adam could have been declined, altering the outcome for him and the rest of humanity if God had simply provided another mate and a deterrent not to follow in the footsteps of the first woman.
4) Both Adam and his wife succumbed to temptation and altered the course of human history.
We can see that God did not interfere with the choices of any of his free willed children.....but simply went about repairing the damage and leading faithful ones back to his first purpose. All will end well, and in the end, no matter what choices they made, God would have responded with a solution. 
