Pulling a 5th wheel RV trailer with a 1/2 ton.

IMHO, pulling that much trailer with a half ton is asking for trouble. It might be able to pull it, but of far more importance is being able to stop it and control it downhill, on curves, or in an emergency braking event. A half ton is fine with a smaller utility trailer. But a 5th wheel with its higher wind profile and center of gravity it's likely to put you in a ditch. I'd want a 3/4 ton minimum for what you are planning. Just my thoughts from 40+ years in trucking pulling all kinds of equipment and trailers.