The first key to understanding Job is to know that Job’s destiny (as is the same for all of us) was to be a son of God. All the suffering he endured was to mature him and prove him to be that son of God.
Job was to trust God above all, and not base his faith on dotting all the i’s or crossing all the t’s.
Job represents himself, all of Old Testament Israel, and all of the Church today.
I have never suffered as Job did. I think only those living in a war zone would come close. But, every time I have gone through difficult circumstances, and trusted God, I came out the other side more mature and more of a son of God than before.
Pursuit of Percipience 
Was Job a son of God? He doesn’t seem to be part of the Abrahamic covenant and God refers to him as a “servant.”
I would argue that the design for mankind to be “sons of God” stems back to creation, and the condition of being a servant is a pre-condition to sonship.