Very well done.

I think you might consider making the "Buy Now" button a bit more prominent on product pages and place it somewhere else so it doesn't look like one of those "Donate Now" buttons. Also, you might consider stating that the questions for the contact merchant form are to help prevent automated submissions, if people don't have experience using forms with these kinds of questions.

Other than that, I think it's a very cool idea. Good luck with it.