OK. I'll use worst case situation - all tanks are full.
863 lbs fresh, gray and black water
176 lbs LPG
341 lbs gasoline
Total - 1,380 lbs + 430 lbs (us and dogs) = 1810 Lbs
12,000 (PC2910) + 1810 lbs ( worst case load) = 13,810 lbs
With a GVWR of 14,500 lbs I would have a 690 lbs margin
Since I would never have all tanks full (Tom H's comment) it looks like we could safely plan on loading about 1,000 lbs of dog food and wine - maybe some clothes and other essentials.
Thanks all for your comments.