If we purchase multiple pre-paid cards from Costco is there any limit to the number of cards we can use to pay our bill?

No , either a credit or debit card or cash of course.

As long as the bill gets paid, they dont care how many cards u use.

No. I used 3 to pay for a bill in october 2017

No

I don't know about The Dead Fish specifically, but many restaurants are suspicious of using mire cards than there are people in the party.

No, we have used many cards to pay!