With three lbs of sugar you may even go higher.
Expect the cider to ferment down to less than 1.000 unless you stabilize it or crash chill it.
I personally like to add light brown or regular brown sugar, or table sugar with a little molasses, but I usually only add two lbs. If I want to further bump it I buy a few cans of concentrate. The rule of thumb is one can of tree top per gallon will rise the SG by 1.009.
Juice with a SG of 1.045 or so will give you an ABV of around 5.8%. (some juices may be higher).
Adding three lbs will get you around 9.5% ABV if you go to 0.998 like most ciders.
Depending on how high the ABV and dry you ferment it down to extends the ageing time. I have found it takes a very dry cider to take around 8 months to really kick a.., you could back sweeten, mix with soda, etc to match your taste.
Hightest has provided a spread sheet in the FAQ sticky at the top of this section, it is fun to play with and do all your what ifs.
As for changing out the yeast, I would not unless you suspect the yeast is not good. If you buy the kit I would just make it. Otherwise it may be cheaper just buying AJ, sugar from the store an going with that. BTW, that's what I do.
Hope this helps, and welcome to making cider.
In Primary: Belgium Chimay clones.
In Secondary: Braggot, pale ale, end of the world white.
Conditioning: Mead, Cider, braggot, Belgium Wheat.
On Tap: Clones, Chimay Blue, Red, Porter, malted cider.
Bottles: Far, far, too many to list.