I agree you have a potential problem if his estate claims improper distribution / release of funds.
But, I don't know if there could be Reg E. Claims . . . the owner of the account is who can make a Reg E claim & you now have no owner. Can an estate make a claim on behalf of the individual ? I don't know / haven't heard of that. And even if they can, it was an approved access device that was used & with the PIN - - - how could they prove their claim that the owner had not given authority for the use. BUT - does the authority die with the owner ?? . . . WOW . . . ??
I know that rambling is of no help & I too, will be interested to hear what the GURUs have to say.
_________________________
My opinions are just that, and might be worth what you paid for them.