Congratulations!
On the new babes, and the successful finding of a good forever home for the 'extras'.
To answer some questions...
1. Cuttle bone is an excellent source of calcium (they need calcium, so this is good).
2. If you tie that cuttle bone up, it will stay cleaner,and be less likely to get lost in the 'stuff' in the bottom of their hutch.
3. The grinding noise might be your little one clicking her teeth at you. My experience has been this can signal anger, nerves, fear, or a general unhappiness with something happening to or around them. Some do it more, some less, but they all pretty much do it. Don't take it too personally, but you might want to watch what triggers it and move a little more slowly. You didn't mention the lava stone chewing 'ledges' or 'triangles' so I will suggest them. It helps grind their teeth down, and might give you baby needed objects to work out on.
4. Apple juice might be a better choice than cranberry Only add a tiny tiny bit to scent it, if you must add juice to their water (not necessary). Usually apple juice is added to water for a new Mother, to help her milk come in well. Remember, sugar is not your baby's friend, also adding anything other than water-soluble chinchilla vitamins can cause their water to become cloudy faster, and make it more difficult to keep their water bottles clean.
5. IMHO Mazuri pellets are the best, and alternating timothy hay and alfalfa hay is a great idea.
6. Talking snacks can bring a firestorm of dissent anywhere ChinMoms gather. That being said, most seem to agree that PLAIN bite size shredded wheat, plain cheerios, yoghurt covered alfalfa treats, and Rice Pops are an acceptable list of treats. Dried kiwi, strawberries, and apricots, and raisins won't kill them, in very small amounts - but you seem to be aware of this.
I'd say you have a very good idea of what you are doing. But I couldn't resist chiming in anyway.
It's just me, Cerberus and Persephone's GrandChin
The more I learn, the more I realize how little I know