Well for starters at least the vendor has far better than average feedback. That has become so important that I would not consider getting involved in a deal reciently on a 1991 300d because of the few negative remarks posted on the vendor plus his private auction b.s.. I kind of thought the pre purchase inspection if allowed would kill the deal anyways. Just too slick as well.
I really believe people in general do not leave negative feedback unless really upset. I know there are exceptions but just generally speaking.
You know the vendor then is going to respond negatively almost always with no reason. You were the victim after all not him and he knew that.
This vendor seems to be pretty knowledgeable about his car perhaps a plus. There might be a member close by that could have a look for you.