What's the comfortable weight limit

Remember that dry hitch weight can be misleading. You do have to take into consideration what that 5er weighs loaded with people, things, water, propane, etc. Also, hmknighnc said is correct. you will be overweight before getting into the cab. Don't for get that you want fuel in the truck as well as passengers, etc. If you plan on the minimum, you will short yourself. Overdoing the axle weights does mean that you could exceed your tire weight rating. That would be dangerous. You do need to weigh that thing on every axle and then combined to ensure you are ok.
I wouldn't take a chance on 17,000 lbs with a 2500.