If it was me I would give his money back to this guy (with proofs) :
Ok so it looks like this motherfucker owes me 3.25btc. 3btc I deposited to nextponzi and before I got it back the site was gone and 0.25btc I deposited to bit-dividends. How do I claim my money back? I have my old wallet ready with proof of transactions. Who should I contact?
And then half of the money back and the other half to a charity of your choice.
This guy is a serial scammer. He is part of what makes BTC so toxic. Let's do some good with his money.