Sounds like you are making some progress in figuring things out.
To get your payload capacity you want to take the GVWR figure from the sticker on the door jamb and subtract the scaled weight of the TV. To get an accurate available payload capacity, you want to include anything and everything you would have in the TV for a camping trip including a full tank of gas (esp. if pushing things). And when going through the scale with WDH dis-engaged, you want the spring bars in the back of the TV.
The number of pads at a scale is irrelevant as you could get all the info. you needed even if there was only one pad. Gotta make the 3 passes - TV only, TV + TT & WDH engaged and then TV + TT & WDH dis-engaged. You could do the TV only any time without the TT. If you are near a highway commercial truck scale, you could weigh just the truck there since those scales are accurate.
The following may help:
learntorv.comLearn to RV"How heavy a travel trailer can I tow?" by
Changing Gears calculatorAnother calculator plus info:
fifthwheelstWhen you have all the scale numbers done appropriately and TV ratings, just post them and someone will help decipher them.