I'm not going to comment on the bug itself as no PoC has been provided (I don't think it's ethical to post it publicly without the casino's consent, anyways).
However, I wanted to salute you for your honesty and reporting the bug instead of exploiting it and milking the casino's wallets dry!
I also wanted to share my opinion on your second question:
How does someone go about reporting a bug to a casino a still hold casino accountable to pay a bounty?
You can't hold them accountable especially if they don't have a bug bounty program. Even those who have it but don't want to pay you can claim it's
a duplicate and reject your report.
that is true, check the section of the terms regarding bug-related protocols for the site. because if they have, they have certain requirements to comply with. because not all sites have their rules on this bounty. however, for ethical purposes, one can always contact their support and ask for assistance about such concern. it is your conscience that will direct you if you will tell them about your discovered bug or just siphon their vaults for your own pocket.
In summary to that, that thought only exist in your head, since the BC game team have seen that your reports for nnthe bug is not worthy of any attentions and how best you are truthful to yourself, and if their act as if nothing is wrong with the system and there is no bug which their have not stated any ways, but be sure that the only way we can believe you is when you share some screenshots since you said you have some of them at your disposal.
Any ways, I think the best way is to try more to get in the touch with the support and hear their own side of the story, but also note that when a player fine a bug in he system, it is noble enough for them to report the said bug the the team instead of exploting them
i believe it is his own disposal if he is true to intentions in helping the site about the bug or not. because let's say the site is not giving some incentives, are you going to submit your discovered bug or are you gonna exploit it? now, that is for you to contemplate about. because if you reach them and not reaching back, and you feel your time is being wasted, then, it is for you to decide what to do with the bug you discovered.