I found this, but can't remember the source. I am sure you can find a chart somewhere that will give examples of other bottled/carbed products and what their volume equivalent it.
1/2cup of granulated sugar is approximately 100 grams. It only takes 92 grams to carbonate 3gal of a wine that fermented at 70F, to 3 volumes of CO2
As far as the stoppers, I had been told by LHBS that you can opt to use champagne cork stoppers or the plastic stoppers, or Grolsh style swing tops.