Did Job choose the path he was on, to take on so much at once in order to get it over with, or was this all a consequence of the karmic forces lined up demanding restitution?

He chose the path to be out of divine alignment, and that is what sealed his fate, that he made poor choices and this caught up with him. It created the karmic energy of discord visited on others and on himself as well, and it was that discord needing to be set right and the energies rearranged accordingly, to give back a repayment of healing energy to right the wrongs of the past, in effect, that were his burden and obligation to see to. So he chose to be expressing human failings and the Law of Karma mandated restitution, and he was forced by the consequences of those energies to suffer grievously at times, and in event after event heaped on him. This was all to teach the lesson of his past mistakes and to experience them directly and personally as the object lesson to make it quite real. Experience is the best teacher and, if nothing else, a taste of one’s own medicine will drive the point home like nothing else can do. That is the wisdom of this system of divine rule enforcement—it is dispassionate and evenhanded because it is built into the energetic fabric of the universe and not left up to the whims or arbitrary judgment of anyone, including Creator. This is its wisdom in a nutshell—that it is a perfect self‑functioning regulatory mechanism to keep the universe in order.