1. You can use one thermostat for multiple tanks. (I think that is what you are asking) ONLY if they are all the same type of heating device with the same wattage and if they are all in the same room with roughly the same ambient temp in that room. You can also use rheostats but you need a somewhat constant temp in the room for them and a heat gun to monitor them. I actually prefer a rheostat over a cheap thermostat. I never had luck with cheap thermostats.

2. I do not like heat lamps and do not recommend them.

3. Never have used them. I run with racks but back in the day when I had tanks I would just manually mist.

4. These are the bowls I use. http://www.reptilebasics.com/water-bowls Again I use racks though so I don't care if they are fancy or not. Someone else might be able to help you with nicer looking bowls.