Basically, what you need to do now is withdraw all funds and drop your bank account and all cards from paypal first...you can add them back later if you want. You should have the device serial number and if not written down, check your apple's devices pages. Then have him send it back...check it out because they may just wanted to return it, they may not ship it back...make sure they add tracking, or they could swap it out for parts...you should notice this. Make sure it is insured as well.
You can't consider it a scam until after the return is executed...if you don't get the device back, that's the first part...that's where insurance will help you. If something else comes back or an empty box, that's where the difficulty begins.
From here, you can either eat the loss, or fight this. The first step of fighting it is SUBMITTING A POLICE REPORT of theft and fraud (include all buyer information such as address, name, phone, and email for history reporting). You can also report the fraud to the FBI as that is their field directly. If it is in the US, this makes it easy. When that is done, submit a copy of the police report (and FBI fraud report if they actually give you something) to Ebay. All all the details from the beginning here...if they choose to side with you, here is where they might.
Now eBay will probably still side with the buyer despite "seller protection" so they will tie the cost of the return to your account and it will go negative at this point. This leaves you with the option of either paying it to zero or never using the account again. Here, you'll need to do your research via google to decide what you will do. In short, eBay cannot file a credit penalty on you, but they can submit a collection agency after you.
You can finally win this credit agency battle at this point. Do some googling. You essentially will ask the credit agency to provide the written evidence provided BY LAW. Timing is everything...making it drag out...again, research this. The collection agency cannot collect until this is provided...they will go back to eBay and request this...ebay already takes too long at this in the first place and will submit it outside of the collection agency's deadline and the credit will fall to eBay at this time and you'll be in the clear. They will probably not allow you to use paypal again so you will be at a loss there. When I say again, I mean until the statute of limitations expires on this which I guess is 7 years.
eBay recently changed the timeframe to contest to 1 year so I expect a class action will eventually force them to prevent fraud. I hope this advice helps.
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That is ridiculous, eBay is completely broken.
Read my post...it should help you out.
Family, holiday, friends. You have lots of reasons to feel good about what's going on in your life, other than this guy. The worst thing to do is let him spill his bad karma over into the rest of life. 
