Heres my take on it. You gave him an offer for a product at a set price by a set time. When he paid the deposed that became a contract. Unless you have papers stating that he agreed to a new price or delivery date when he changed the design you are still to meet that delivery date. If you fail to meet the delivery date or the delivery price without proof you both agreed to a change in contract he has the right to a full refund. The court will see you as being in breach of a verbal contract. You may be able to get him charged for something because of all the bickering but that has no affect on the original contract.