The numbers/towing parameters are calculated by the manufactures. You can believe them or you can ignore them.
At the end of the day a combo that is within all of its ratings will be more stable than a combo that is within some of the ratings.
They do make trucks to tow that RV that will be within its ratings.
Do you want to use the correct truck or do you want to fudge it with what you have. Fudging it is OK within reason, as long as you understand what you are doing.
If you are not comfortable fudging it. Be sure to match your combo so that it is within ALL of the towing ratings.
Tow ratings are not so much for clear sunny days when everything is great. But they are for bad days when conditions are bad.
Cars come with spare tires for a reason and planes have life jackets on them for a reason. Engineers and designers are well aware there will be bad days.