Hammamet is a good base for the north and the Sahel, and a poor one for the desert. Carthage, Sidi Bou Saïd, Kairouan and El Jem are all comfortable day trips. Douz, by contrast, is about 388 km away in a straight line — that is an overnight trip, not a day out, whatever an excursion desk may suggest.
No. Hammamet to Douz is roughly 388 km in a straight line and considerably more by road. Two days is the minimum, and three is more comfortable.
Yes, easily. Carthage, Sidi Bou Said and the Tunis medina fit into one comfortable day from Hammamet, with time for lunch on the terrace.
Close enough for a day trip, and usually combined with Kairouan or Sousse on the way back rather than driven there and straight home.
Distances are straight-line, measured between the coordinates on our map of the sites; road distances are longer. Prices are per vehicle and come from the same database the 28 tours and 1,392 transfer fares are quoted from.