Hotels and alternatives
There is a basic hotel-thing in town (called "station touristique") where you can get an authentic, if rather un-luxurious, night's sleep.
Restaurants and alternatives
Eat in the tourist station.
Nothing. Do this in either Medenine (75 km) or Tataouine (85 km).
There are no forms of public transport between Beni Kheddache (on the Medenine-Tataouine route) and Zammour, and even less between Zammour and the ksar (2 km on rough road). Hitch all the way from either Medenine or Tataouine (difficult), try to get seat(s) in a shared taxi (also difficult), or hire a taxi for the day (a bit expensive, about 60-70 dinars.
Once you have gotten as far as Beni Kheddache, the rest of the trip can be done on foot you will pass through a very nice landscape, and half the way you will pass a café overlooking the valley of Beni Kheddache.
Further ahead there is a turn-off to the left going up the mountain. Just pass this and continue down to the village. You take the largest turn-off there is to the right (before the tourist station), head up about 3-400 metres, and then take the rough road once again to the right. Follow this straight ahead, and you can't go wrong.