My cat cries and scratches at the door all night. How can I sleep?

It sounds like you have an active young kitty cat! Well, unfortunately, you are doing many of things I would suggest for you to do already. However, we have not yet exhausted all of our options. It sounds like Ginger is experiencing some level of distress, whether or not its due to separation or a need for attention is very hard to say. I would consider adding some Feliway Diffusers into the home. They can be found on Amazon or at a local pet store. They send out pheromones into the environment that aim to calm the cat. They also make direct sprayers that you can put onto objects or even directly onto the kitty himself. If this sort of thing works, it usually doesn't happen overnight. Another option, which may not be possible and might sound insane, would be getting a second kitty. Ginger just may need a friend to keep her company when you aren't around. There are also pharmaceutical interventions that can be given if what Ginger is experiencing is truly anxiety. A behavioral work up by a trainer or vet at your home would be very helpful in this case just to get a full idea of the entire situation. I hope one of these tips can give you some peace at night.