Firstly, your stem is that long because it is stretching for light. The sunlight you get through your window isn't going to be enough for it. You should get yourself a couple cool white CFL's and start from there.

Cutting off the stem will kill it. No leaves will grow back. And with the kink, I'm not sure its going to survive at all, since its so young. Its worth a shot I guess but you really do need to get some lights and get them close to it. Within a couple inches, but not touching it.