does anyone know what a casino tells the department of justice about a patron of theirs.?

I use to work at a major Nevada Hotel Casino, I was in the Tax compliance office and we told the department of justice nothing unless there was a court order to do so. On the other hand we told the irs all about customers winnings all the time.

They can tell them anything they want to tell the DOJ. If they don't/won't do it voluntarily they would to it under a court order.

Nothing unless asked with a subpoena.

Nothing.
Unless the Casino feels you have cheated them, then they may file charges but in the United States, the Department of Justice would not be involved. This would be a local issue handled by local police.

Keep in mind, the Casino makes money by providing a great fun place to gamble. They are in the entertainment business. They are focused on luring you to their business. They are not in the business of cheating, stealing or having their customers arrested; bad for business.