The theft of the 88 ETH occurred within ten minutes of my withdrawal, and only two parties were aware of this significant transaction: myself and Bitcasino.io...
No, you're wrong. An unlimited number of people knew about this transaction, since all transactions in the blockchain are visible to everyone. At the same time, attackers use bots that signal all large transactions on the network and it is obvious that your 88 ETH belong to this category. Bitcasino responsibility ends from the moment this transaction for transferring funds to your wallet appeared on the network.