In my opinion, Such a very large amount of gambling losses like that on a regular return would significantly increase the chance of an audit. Now if you put that on an amended return, which  may be scrutinized, then I would say there's even a greater chance of an audit. Years ago a tax professional told me one of her clients were audited for gambling losses and they wanted to see all of the receipts/tickets/documentation. And the amount of gambling losses was far less than the amount in your situation. But that is my opinion, and you do what you want to do.