Would love to see that mail chimp option. Also I'd like to have more images. Why not use some images form unsplash, little visuals etc. I remember a hn post couple of weeks ago which had a list of stock photo with a license attached so that you could use them.
First, start compiling all the documentation you have (emails, screenshots, invoices etc.). Also start explaining your side of the case in writing. Then I would wait how PayPal reacts and what information they want.
In the meantime source some lawyers you might want to speak in case you lose. Additionally you could file a case with your local authorities.
Second, use an escrow service in the future. I don't know where you are located but for
US/Canada transactions I can recommend http://www.escrow.com. Within Europe use http://www.eco-treuhand.de