I don't think anyone's in a position to conclusively confirm or deny your speculation on LW-participant demographics, although you might find useful the link to the survey results jimrandomh posted above.
OB is Overcoming Bias, formerly a blog on rationality with multiple contributors, including Eliezer Yudkowsky, now the personal blog of Robin Hanson.
The only data on maths/science knowledge in the LW community I know to exist can be found in the aforementioned survey results. It is probably out of date.
"Right-extremists" is probably not a helpful way to think of how the term "libertarian" is used here. It refers more to advocacy of individual liberty than a position on a classical 1-dimensional political spectrum. I wouldn't describe myself as a libertarian, though, and I'm certainly not an authority on them, so other people are probably better-placed to answer that question.
"Singularity" is probably a bit too big to elaborate on in a couple of sentences, but it's conceptually distinct from libertarianism. I like to describe it as follows: there are technological achievements which we know to be theoretically possible, but which, if developed, would entirely rewrite the rules by which human beings exist. I don't believe this is comparable to the wunderwaffe concept.
I've been lurking on LW since shortly after it started, and on OB for about six months before that. In that time, I've told four or five people about it. I would make a terrible evangelist.
I'm curious as to whether other people have the same problem. I'd like to tell lots of people about LW, but I don't think they're ready for it. If they read a statement like "purchase utilons and warm fuzzies separately" their eyes would glaze over, and they'd walk away thinking LW was some sort of crackpot site.
I have found certain posts and topics to be fairly good hooks for getting people interested. An Alien God is a good suggested read for people with an interest in evolutionary theory and the Cthulhu mythos (surprisingly high crossover in my experience). HP:MoR is also a pretty popular hook. The site itself isn't really optimised for word-of-mouth, though, and not everyone likes child wizards and blasphemous horrors.
How many people have you introduced to LW? Who were they, how do you do it and what was their reaction? How could we do it better?