There no minimum or maximum. You need to feed as much as a frog can eat once a day, every day. They are pretty good at regulating their food intake and as long as the food is healthy they won't get overweight.

Keep in mind every frog, just as every human, is different, what is true for one, might not be the case for the other. It is important to react to what frog is "telling" you.
usually babies will eat every day, when they are about 2-2,5" they would refuse eating every day and may choose to skip a day or two, adults may eat once a week, but once again each frog is different.

so you need to offer food every day and properly supplement it, as they grow at some point it will turn to be every few days feeding.

the reason for cutting worm is that when a frog is little the whole worm is too big, small pieces will let him stop when it is enough.