I have slept for that long on some of my fasts, so don't worry about it, and Shelton says take as much rest as possible. It's probably bringing your stress levels right down!
Try and move around a bit now and then though, keeps the lymphatic system going. A short walk now and then perhaps.
Cramps - I get something like that, does it feel as if your muscles are trying to suck energy through a straw? That's how I would describe it. Its probably quite normal. I expect you feel slightly light headed if you get up quickly to.
Sounds like you are doing fine, relax and enjoy the rest!