Regarding carb level, it's completely up to you. Some people enjoy more carbonation in a cider, some people less. If you're using thick-walled glass bottles or plastic bottles, you can probably do above 3 volumes, but otherwise I'd keep 3 as your max. You don't want the bottles to explode! And that's the total carbonation, including residual post-fermentation CO2.
If you input "3 volumes" into that calculator you linked, it will give you the appropriate amount of sugar to get a total of 3 volumes including the residual CO2.