GVWR is something that needs to be considered separately from GCWR.
You don't want to be over your GVWR at any point, even though you might be under the GCWR.
GVWR is based on suspension components, tires and axle ratings.
Theoretically I could load my Coach to exceed my GVWR and be under my GGWR.
You must also consider your towing method. Towing 4 down and you're not adding much to your GVWR. If you're using a tow dolly you're adding to your GVWR.
To figure your CCC you need the unladen weight of the coach. Your math is wrong because you're using the GVWR as the weight of the coach. My Winnebago loaded for travel is 23K and that's on a 40ft Coach that has a GVWR of 26K.
Ask to have it weighed before purchasing.I suspect your unladen weight will be around 23-24k lbs.
With 900+ lbs left over after using incorrect numbers you'll be fine. You'll probably easily have 3-4 thousand pounds of real world CCC. Which you'll find out when you get the unladen weight.