1. If that person doesn't want to sign a message with the key of one of his early Bitcoin addresses, the world will not believe you.
2. From the answers you got, he doesn't want to do [1]
3. All this being said, whatever you add is something between scamming and begging. And the "send me 1 BTC and if you are not happy I'll send it back" part is pathetic indeed. Bitcoin transactions are irreversible and I've also seen no honest scammers yet.