Apparently Friday was a day that they were working on merging the seat maps and there was some difficulty with some of the DL-NW back and forth stuff. Sooner or later they will get it worked out but I am not surprised at the trouble the OP was experiencing that day.

Looking at Expert Flyer, even at a week out one would think that the OP has an excellent chance for an upgrade. A call to either DL or NW should get him one of those good seats but it is also even possible that the phone agents are having some trouble with seating right now.