Welcome Ellie. As Alan says, they can take a while to settle as torts do not like change. The baths, the basking temperature and cuttlefish all sound good, but little hatchlings do spend a lot of time sleeping and burying down.
The Tortoise Table is really helpful for safe food ideas
https://www.thetortoisetable.org.uk
I tend to use nutrobal at the weekends only and sprinkle limestone flour during the week.
I’m sure you have a temperature gradient so he has a cooler area, hides and so on as it sounds as if you’ve done some research.
If he’s excreting, he’s eating a little so try not to worry and I’m sure the little one will soon settle in.
Please let us know how you get on and remember, no question is a silly question. Ask away if you’re not sure about anything.
Plus we love names and photos.