I'm confused... He has a great rep here
He's been here a few months, has only a few trades. How is that great rep? Why would you risk that much if you know his profile and reputation is not worth $280? You've been here long enough, but still made a newb blunder.
Call Green Dot and report the card. Tell them you have the physical card and receipt you can take a picture of. They'll probably void the balance and ban his prepaid card or paypal that was used to load the MP. However, don't expect to get a refund from Greendot or CVS.
Harsh as it sounds it would be a negative if they did refund you... horrible as it sounds people have to learn the hard way that escrows are essential here. You say you've been scammed before why on earth would you do this trade as you did yet again? Learn something this time.