I wouldn't say your number 3 above can be considered mainline.The Rabbis basically took into account the entire body of Torah, not just Genesis 9.
Scanning some of the online information about the Noahic laws, a few things stood out:
- The "don't eat flesh torn from a living animal" made me internally go "WTF? Who does that anyway?", but by extension, it's considered specific case representing a general prohibition against cruelty. There's a literary term for that which escapes me for a moment. Ah. "Synecdoche".
- The general context for these laws for the Talmud's Jewish audience is, "Who is the 'stranger among you' that Torah requires we protect (which brings to mind a question someone once asked another Rabbi, 'Who is my neighbor?'), and what are their obligations when living amongst us?"
- The Jewish sages wrote that Goyim who live according to these laws will be considered righteous and "have a share in the World to Come". A Jewish answer to the question, "What of those who are not one us; how can they be saved?" Compare with the mainline Christian answer to that question, which would be, "Sorry, Charlie. Burn, baby, burn!" Do our Jewish cousins believe in a more merciful God than we do?
I have no statistics, but I find that only holiness churches or fundamental churches believe all non-Christians will go to the other place.
Maybe it's right to state MAINLINE.....I don't know.
Do you have any statistics?