It's best to break-down different projects:
Ask SAT questions here:
http://www.irv2.com/forums/f53/
Ask generator questions here:
http://www.irv2.com/forums/f54/
The overall RV is basically a normal E450 with the bedroom stripped and a heavy duty floor in it's place, so questions can be asked here (owners forum) or in the Class C Forum:
http://www.irv2.com/forums/f87/
To figure the max towing capacity, you must know the Gross Combined Vehicle Rating (GCWR), but even if the RV is well below the GVWR, you cannot exceed the hitch capacity.
Best luck and safe travels