Is the 1/2 teaspoon of yeast for the sponge enough when adding the additional flour for the dough to the sponge?

For a long, slow ferment like a sponge or an overnight pizza dough, a small quantity of yeast is surprisingly effective! Plus, the long slow ferment is key to developing flavor.

People tend to forget that yeast is alive, and constantly reproducing. A small amount of dry yeast will suffice if given time and good growing conditions.

Yes, it is!