Digging and Biting

Question
I currently own three ferrets. I have sisters Apollo and Nova who are both right around 2 years old and Cosmo. He is my newest edition and he is 10 months old. They all get along wonderfully but I have a few slight issues with Cosmo and Apollo's behavior sometimes.

Cosmo has this horrible habit of digging. I understand it's complete instinct for ferrets but every time I put fresh litter and even food into the cage, he immediately digs it all out and it's fairly frustrating since most of it gets kicked out of the cage. Is there anything I can do to prevent this?

Then Apollo. The other two have no problem sleeping through the night but she is up every couple of hours or so and becomes restless. She goes between scratching at the shelves or bottom of the cage, or biting the bars of the cage. I know she wants out but I need sleep! I generally try to let them out for an additional half hour before I go to bed but like I said, she just will not sleep. I know giving into her reinforces the behavior but I get so worried sometimes that she will break her teeth on the cage. I've considered buying a bitter spray but I know they have sensitive digestive systems and I wasn't sure if it would make her sick or not.

No complaints on Nova, she's perfect. The other two should learn from her. Haha. Anyway, I appreciate any help I can possibly get!

Answer
Digging: You can offer him a safe and fun place that he is allowed to dig using play sand.  You can also try using a litter box with higher sides.  Same with food - use a heavy dish with higher sides.

You can try Bitter Apple spray for the cage, but you nailed it - she knows you will let her out.  You are just going to have to wait it out until she realizes she is in for the night.