I don't trust Wikipedia, and I take everything I see on there with a grain of salt, so to speak. As for the JEwish thing, it is possible that people ar just going off Hillenburg's last name, as 'burg' is often a Jewish suffix. But really, just because the creator is Jewish (if he is) doesn't mean that his creation will be as well. As for the Christmas episode, many people write Christmas themed music/stories because they know it will get more aire time and be more popular than Hannukah themed shows--think of Irving Berlin's "White Christmas"--it wasn't "White Hannukkah" (actually that would sound a little weird!)
Regarding the gay issue, it may be true that some people see him as an icon as such, but that is their opinion. Recently, I haven't heard much since the controversy died down a few years ago.