I’m probably closer. Where does he live?

In all seriousness, play his game as another commenter said. I have a similar family member (though they have no money to begin with) but my argument to them is banks can fail hit government won’t let that happen - see 2008 bailouts. Maybe you could do something similar.

If nothing else, next time you go visit, rent a small truck and get him the highest rated fireproof safe you can and help him install it. Renting the truck means no delivery people know. You buying the safe means no one with your information can easily connect the dots back to your dad. The only worry then is people seeing you unload it and you might be able to solve that with a used box from a furniture store or home improvement dumpster.