spinhub probably can't believe you actually went and provided them those 20 documents... that kind of hurdle would put off almost everyone. and in addition to that they could nit pick in those 20 documents that something is not clear or missing.
after more research your realistic way out is to stop trying to force OKX to accept the money. they won't credit gambling funds, you gotta shift to getting OKX to reject and return the transaction, tell support you can't fulfill the travel rule sender requirement and request OKX to reject the transfer and send it back to the sending blockchain address. Also you gotta message the casino before the bounce and send them the TXID. once it's back in your casino balance then cash out to a private wallet.