You don't have to sign from your current address. The wallet you used to withdraw in 2014 is enough to prove what you say. Even if it is now empty.
I doubt he will actually do that since it seems like he is craving attention which is why he conjured up this wild story basically.
If the casino bans the OP, he can just create a brand new account and do that again, so the only way for the casino to prevent the same occurrence is when they improve their website's security.
Firstly, I think op is full of crap. Secondly, if he's actually saying the truth in this case, the incident happen so long back and the casino in question would have already drastically increased their security if they are still up and running.