Welcome to the forum & irv2.
Here is a Brochure
should give weights and tank sizes and Owners Guide
for the 5th weight & towing info..
The CCC would be the GVRW WEIGHT 16,250 less the full fresh water tank,hot water heater, and the full LP tanks that's left over.
The tires if taken care of properly, good tread even wear and no sidewall cracks should be OK for now.
Check the suspension and tow overhang portion of coach to main body of 5th wheel.
Good luck and safe travels.