I have a very good friend used to bring rum balls in to work at Christmas. "Look out" she would warn us, "Just one will put you on your ear."
The average rum ball is 10-15% rum. (Except for Aunty Vera's which were 0.001%)
The average shot of rum is 30ml, one standard drink.
It takes 5 standard drinks to get you to the legal maximum blood alcohol level, 0.05%.
That means you need to eat two kilograms, or nearly four and a half pounds, of rum balls to reach the the point where you are considered unsafe to drive.