5 grams of yeast would usually be just fine. (or half packet as jackfrost recommended)
As for hitting a target ABV, without accurate gravity readings you may never know. If you want to forego taking readings, I would suggest fermenting a batch with no sugar...then add a half cup (per liter) on each batch after that until it gets to where you want it. Having a baseline will help tremendously in future fermenting.
I usually use a cup of lt brown sugar for 1 gallon of cider. This usually puts me in the neighborhood of 1.060-1.065. If I let it go all the way dry (1.000) that would be about 8-9% ABV. The more sugar you add, typically, you'll need to let it age longer and let the alcohol flavors mellow and the apple flavor to come back.