Looks like a few things need to be corrected...
He died of lung cancer due to smoking. While it is potentially (though baselessly) arguable that he may have smoked more during WWII, he still would have predeceased Edward.
Not necessarily. They both smoked, they both died of smoking-related cancers, but a very significant difference was that the Duke of Windsor led a far more stress-free life than George VI. It's quite possible that George VI would have lived a decade or two longer if he'd had the easy life that the Duke of Windsor had, and it's quite possible that the Duke of Windsor would have lived a shorter life if he'd had the stresses of kingship to contend with. Since we don't know one way or the other, this isn't a factual matter that requires correction, Mr. Know-it-all.