help with weight calcs

The calculation is done static (level not moving). That is not going to be the Dynamic, (going down the road), max load which constantly shifts. The height of the camper and the Jeep, up on the flatbed, will act as a pendulum, extenuating the loads even more. This then requires assumptions that can be done, but probably would be best for you to go to an expert, in custom buildups for rigs like Heavy duty emergency or military trucks. Probably higher rated springs, sway bars and tires are needed, maybe even brakes.