I have nothing at all in this, but I have read the whole post and I think mr Firebird should just quit bad mouthing you.
We have all sold cars and regretted it, but I doubt any of us has tried this sort of shananagans to make the deal better.
It seems that Wayne bought the car for 13,500 and has the bill of sale to prove it, what is wrote on firebird's bill of sale could be done by anyone at anytime.
The only question I have is to Wayne, does your signature look like the one on firebird's bill of sale? Or is it a forgery?
Thats my .02