First of all, what kind of "cider" did you start with? Ideally it would be raw apple juice/must, fresh from the orchard, non-pasteurized and definitely without preservatives (like potassium sorbate, which largely inhibits fermentation). You can get by with pasteurized juice/must, but it is more difficult to clarify later (pectin haze).
Secondly, what type of yeast did you use? Were you relying on the wild yeast present in the apple juice/must (which is a crap shoot in terms of flavor profile), or did you kill that with Campden tablets and let it sit for 1-2 days before adding the cider- or wine-specific yeast? Champagne yeast works well because it is very tolerant, but it doesn't impart much taste. Red Star Côte des Blancs or Lalvin 71B-1122 Narbonne or Wyeast 4766 Cider Yeast or AWRI 350 Yeast all have better flavor profiles.
Third, did you rehydrate the yeast according to the package instructions, especially temperature? Did you add a rehydration nutrient? How warm was the room where you were fermenting? Room temperature is usually just fine, but any colder and it inhibits fermentation. Did you add the yeast to 2-3 cups of juice/must as a wine starter in a warm location to ensure the yeast had taken hold? If not, any residual wild yeast may have taken over, and it is far less predictable, and far slower. Did you add a yeast nutrient when you added the yeast starter to the rest of the juice/must.
The amount of bubbling is only a rough approximation of whether fermentation is still continuing. A change in specific gravity is the only real test, which is complicated by trying to use a refractometer to measure specific gravity instead of a hydrometer. Ideally you would use the same hydrometer at the beginning and end of fermentation to measure the difference.
On average, it took my ciders about a month to ferment to complete dryness (which often was less than 1.000 SG; sometimes as low as 0.980). Some ferments took 2 months to complete. The cider progresses as fast as it does. I used to belong to an international cider forum, and they were always preaching that having a slow fermentation yielded a better taste profile.
I usually only chapitalized about 1 pound of sugar to 1 gallon of juice/must to reach a SG about 1.080, which would yield about 11-12% alcohol. If you add more sugar now, it would be much more difficult to estimate your alcohol percentage.
Of course, it doesn't turn into Apple Jack until you freeze it and extract the concentrated alcohol (which isn't lawful in all jurisdictions, BTW).