Ya, several thoughts:
#1. Wind buffet and sway are tow entirely different things. Wind buffet will hit you and push you around but will end after a few cycles. Sway will start and the cycles will get worse unless action is taken.
Which type do you have?
#2. Out of all the figures you have you don't have THE most important. Tongue weight. Tongue weight (or lack there of) causes 95%+ of true sway issues.
Get the actual tongue weight and get back to us.
BTW, I have towed tons with just a ball hitch with no problems as long as the tongue weight is correct. If the tongue weight is not correct it tows like garbage.