Doesn't make sense how it shows it was delivered, but as in Decado's position, his package was delivered but nothing to be found in the box. Different situation, but you gave him the benefit of the doubt. You sending more parts to him in replacement for others was generous, some people would have said screw you. Him wanting his money back and sending parts back to you is BS. I wouldn't do it. Been in that situation before locally. You're not Wal-Mart, best buy or some sort of chain store. You did more than enough, you sent more parts and additional $60. It's not your fault he's unhappy.
IMO: He's being the dick because you have tried acommodating him twice. Don't feel bad. As a seller I try to make the buyer happy, but I've been screwed a couple times being too nice. If they are not satisfied with the product with the said description, that is their problem. They can go find product elsewhere.