This thread is so long, I can't possibly read all of it now. Just a suggestion; check with your local university library to see if they have any of the wonderful holdings listed here. Many times they do and you can copy the songs your would like rather than buying the whole thing for just a few songs. The music librarian might be of good assistance.
One suggestion: The Dulcimer Chord Encyclopedia is indispensible for any serious dulcimer player.