Standard sprocket on the front is 14, think it could be 49 on the back. I'll check the specs and let you know if it's any different.
As far as stability goes when I first got mine, I had a couple of hairy moments cornering - small amount of wobble - but I'm guessing that was my lack of experience and perhaps fighting with the bike. I quickly learnt to lean further into the corners as opposed to 'steering' into them. Somewhere on here there is a thread on counter steering methods, but basically, forget driving a car, if you want to turn right, imagine a piece of string at 45 degrees to your handle bar and push down into that on the right. If you are leaning with the bike, your centre of gravity will be lower and you should find tight bends smoother.