Judging on the year and the amount involved. This is probably Primedice since there are only few casino back then that have a bankroll like that. Besides there’s news before that PD got hack with the exact amount and during that year.
And besides, if I was him, I possibly would have done exactly same thing, which is, register a new account to share this type of information, for there could be a million ways to trace back to who he is if he had used his main account - trust users of this forum on that, most especially, if he had done the wallet signing most of us do for the security of our accounts, or participate in a signature or bounty campaign in the past, wallet address he used for this activities can easily be tracked or traced, and by so doing, there could be a way to find a link to his current wallet where the stolen funds are held, and this could jeopardize everything for the op.
If I was op, assuming all he said here is true, I will not have bothered creating this thread, it's absolutely not necessary.