I read nothing in Mr. Chamberlain's letter which indicates he asked you for anything. Your reponse to him was not appropriate. He asked for information in an open forum and any response should be in this same open forum. It matters not a whit if his email address is incorrect. And asking for $100 in cash is very out of line, inasmuch as he did not ask to contract you as a genealogical researcher.
I suggest you apologize to him for what seems to be a gross misunderstanding on your part.