Base weight is 4274# from the website you gave. The actual sticker when it left the factory probably more. Add some food and gear you're around 5,000# possibly more. 15% of 5,000# is 750# hitch. Add 615# for family and you are above the listed cargo capacity by 15#. That does not count the WD hitch, bikes or any firewood you toss in the bed.
Load the family up and go weigh your truck then you'll have real numbers to go RV shopping with.
Good luck and enjoy.
2012 Sundance 3100RB w/Reese Goose Box
2004 Ford F350 6.0 L PSD, CC, DRW, long bed, B&W drop ball hitch, Firestone Ride-rite air bags.