Wayne,
I was waiting until you got your read on this oil. Your iron is high, but not over the limit that Cummins allows. I still would not exceed 10-12K on this oil. Personally, using this truck pulling that load, (possible exceeding your CGVW) and running with constant boost unless you are going down hill or idle, it is hard to fault the engine or oil. Short of spectacular comes first to mind. This is my take.