I think the part that puts you in a tough spot is he thinks you were trying to extort him. I have been in customer service management for 20 years and there is a fine line that you have to walk in situations like this. If the feedback is important to you then you need to deliver the product, refund money, and apologize. I would then send an email that you are sending the product with a refund. I would probably apologize 3 times in the email and then at the end I would say that you would appreciate no feedback being left. I would not ask for positive feedback but I would ask for no negative feedback. If you do my steps then there is probably 75% if not better chance of no negative. If you just ship the product without any of the others there is a 50% chance of negative feedback. If you just refund the money then there is probably a 75% chance of you getting a bad feedback. Well that's my 2 cents.