I guess you didn't understand what "The destruction of Sodom and Gomorrah is a certain fact in history" means. Does the author leave any doubt? No - of course not. How are these not real scholars? Or are you just a bitter liar? I knew this one would hit particularly hard for the gay-homosexuals as that is the reason they were destroyed and also the basis for law against Sodomy (Gross!).
No, it is not certain. I can find no source for definitive research.
BTW, there is no biblical reference to sodomy being an issue in these cities. That is an attribution (assumption) that was made in post biblical times.
Maybe do some reading on good sites.