To close the loop on this, I called back today and was transferred to a specialist; apparently applying DSUs to Virtuoso rates need to be handled a certain way that requires manual adjustments or some less than obvious (for frontline CS reps) manner.

Bottom line, the specialist fixed everything and my rate now shows the $179 Virtuoso rate, my DSU was pulled, and the hotel has a suite blocked for me.

I love Hyatt.