[Mr. Adventure]

BamaFlum:
Actually, I don't have a 3rd row seat (that became standard sometime after my model year).

The3ofus:
I'll be happy to answer any questions, but it looks like you've got it by now. Generally, to avoid the need for any algebra or hitching/unhitching on a busy scale, you'll need to weigh three times:
1) With the vehicle hitched, getting all 3 axle weights, and
2) With the WDH bars slacked, getting all three axle weights, and
3) Unhitched, leaving the trailer elsewhere on the lot, just the tow vehicle, both axles.

From these:
Gross Combined Weight is the sum of the axles on either the first or second weighing.
Gross Vehicle Weight is the third weighing.
The Tongue Weight is the difference between the total tow vehicle axle weights on the second and third weighings.
The total trailer weight is the difference between the GCR (either first or second) and the GVR for the tow vehicle alone (third).