3) Besides 潜水,晒太阳,参观石头城, you can take a dala-dala to Jozani Forest Park, to watch colobus monkeys. Or you can rent a bike and cycle around rural villages to watch people...
Another regular tour is Spice Tour in a farm north to the Stone Town.
4) If you buy ticket on FLY540, JRO to ZNZ costs around $150. A budget of $200 should give you the luxury of taking a taxi to JRO.