For tempering, you essentially need to heat the mass up to 120, cool it down to about 81, and then reheat it to about 88. it does not really matter how you do this so a bowl of cold water would be fine, assuming it is sufficiently cold to allow you to get your chocolate to about 81f. you do not need a thermometer to temper, however it greatly, greatly, greatly increases your likelihood of success - for at this time, since you're not accustomed to tempering, you don't really know what success looks/feels like - so the thermometer will guide you.
Local taste preferences vary greatly around the world. in many places in east asia they don't ferment at all. in some places in c. america they bury the beans with lye in the ground. hard to say why a local flavor preference develops the way it does.
The sugar won't heat up the drum at all, it's getting warmer due to the frictional heat generated during grinding. what it is likely to contribute, however, is moisture, which is rarely a good thing for dark chocolate. if your chocolate is very viscous, it's a potential contributor to that.