Thanks for making changes. Were the testing users applicable to normal limits? (ie, are you actually willing to accept 50x kelly bets?)

Could you sign a message from your cold storage address?

Since this is a new website, they should provide evidence that they have the necessary bank roll to withdraw if someone wins and they must be able to provide that proof and if they can do that they are advertising their site, no one is asking to publicly display their entire balance, but they need to prove that they could repay at least 10 bitcoin, the site looks good and if they have the funds its a good thing and it is indeed a way to promote the new site.

This is what I know, any site will not reveal their current bankroll to everyone so there is no way they will sign any address just for their own security here. Big site or small site will no difference, as long as they keep their promise on the payment and withdrawals then I think you do not need to worry about their bankroll because it is privacy that they bet on