I probably won't be the first to attempt to answer your questions, but
here goes:

1) If HBO's series Deadwood is to be believed, 19th century mining towns
were rather vulgar.  They had the same swear words we have, along with
the more antiquated phrases ("balderdash" and such).  I found this site
that seems to have done its research...

http://www.campchase.com/Nineteenth%20Century%20Slang%20Dictionary.doc

As far as Twain's famous swearing, I'll admit I'm unfamiliar with
anything specific, but know of several wonderful sayings on the topic...

2) No, there is not a recording.  Everything I've read suggests that
Edison at one time recorded Twain's voice, but the recording is no
longer around.

Mike Williams