Yeah it sounds like you were extremely patient!  I can understand wanting to do the right thing by someone and make sure they are happy with their purchase which you certainly did, but jeez some people have a hide.  I would have been too embarrassed to continually ring you back like that repetitively asking questions, plus I wouldn't have expected to have the right anyhow to get ongoing tech support.  lol

The second time he tried to renegotiate the deal it would have been alarm bells for me and possibly deal over.  Trying to renegotiate a third time when he picked up the item I would have told him to pi$$ off right there.  That's poor form.