Was Job already possessing “most” of the wisdom needed to overcome his problems, illustrated by God’s confidence in Job’s capacity to keep his divine “partnership” intact in spite of the overwhelming intensity of the experience?

This is a good description of Job’s inner strength, that he was not bereft of reason and resources, and this he gained in his early life where he enjoyed many successes, and it helped to train and shape him to be a good person and evenhanded in his doings, and to have within a good moral compass as well as faith in the divine. All of these are forms of wisdom in action and add wisdom to the mix with every reinforcement in doing things that become a success rather than a failure, and reinforce the teachings of wisdom and the implementation of wise choices. So he had much to work with and this was a factor in enabling him to accomplish so much even though his burdens were quite large. This was no small undertaking and the level of suffering was not overstated here—if anything, it was understated. It takes far less than the actual physical problems he endured to undermine a person emotionally and lead to a life of great torment and suffering. So, to many, the description of what Job went through is almost unimaginable in its power and negative potential to wreak havoc and be life-destroying. So his earlier preparation was the saving grace here, as was his decision to stick with the divine and see this dark time through in the best way he could, that too was wisdom and served him well.