Open the wallet in a virtual machine + a sandbox in that VM (can't be too safe) while running a vpn, check to see if it really has ~51 BTC. If it does take out a 15% fee for the transfer and send him 85% of the funds on the wallet. Nothing to lose, he gets ~43.35 BTC and you get ~7.65 BTC for conducting the transfer. Win-win and your morals don't feel destroyed.