D and J,
On a 5th Wheel trailer 15 to 20% of the trailer weight is on the Pin. The rest is on the axles, for example I have a Big Horn that I weighed, the total trailer weight was 14,000 lbs. 11,400 lbs was on the axles and the weight on the pin was 2,600 lbs.
"What is the actual carrying capacity of the frame?"
It would be best to contact Heartland or Lippert to answer what is the carry capacity of the frame.