Best is to leave the wdh in place but with no tension on the bars. In the pass with just the TV, leave the wdh in the receiver and either leave the bars attached hanging there or if not possible put them in the back of the TV.
You can run through the scales a third time with the wdh tensioned if you want to but its not really necessary. Input all your data into the towing calculator and then (in the calculator) adjust the wdh tension so that the front axle load is back where it was for the TV by itself. That should give you the load distribution you get on perfectly flat ground if you set your wdh up per specs (using the masking tape front suspension height measurement technique). If your whole rig isn't truly flat the load distribution will vary quite a bit though so don't be surprised if things don't match up perfectly.