I just got back from 5 nights out, all above 10,500', 50°F air temps in the evenings, water temps around 40° and a windy environment, I boiled 12 cups of water in a Fosters Cone on well under 4 ounces. And I wasn't watching the pot, so there were times when I used more fuel than required, and I was less than careful when filling and recovering.
Now, at home-
2 Cups of 40° water, a 70° air temp, no wind, 7600' elevation, in a 1.3L pot with lid:
Bubbles at 5 minutes, 'rumbling' at 6 minutes, and boiling (197°) at 7:15 --- ~9 grams of Sunnyside Denatured Alcohol were used. [Edit: 2 tests. 8 grams the first time, 10 grams the second time.]
4 Cups of 40° water, a 70° air temp, no wind, 7600' elevation, in a 1.3L pot with lid:
Bubbles at 12 minutes, 'rumbling' at 13 minutes, and boiling (198°) at 16:00 – 21 grams were used.
You Are missing something big: Caldera Cones work. Design, integrate, test, repeat……
(when looking a volume/weight measures remember that alcohol has a density of .79g/cc, so a gram of alcohol is about 1.25 ml. I'm a weight-based guy. Teaspoons are pretty ambiguous.)