Sold my old rig and starting over -- Need advice!

1000 pound hitch limit is not the payload, it is the hitch limit. The integrated, nonreplaceable hitch is limited to 1000 pounds of tounge weight. It's stupid but that's the way it is. Otherwise, a 2500 Sub is an excellent vehicle.
My suggedtion is get rid of the mini van and get a real van, like a Chevy 3500 passenger van. It will have plenty of tow rating, plenty of seating, and be decent on mileage empty. If you look hard enough you can even find one with a Duramax.