Anxiety is a tough one - but there are some tools and techniques you can teach your DS that might help.
Anxiety BC is a good place to start - they have a good explanation of what it is, as well as tips, techniques, and so on.
https://www.anxietybc.com/parenting/parent-childThere are books for kids about anxiety, but these didn't work for my DD (she felt they talked down to her).
For sleeping, we've used various things - lavender sachets/spray, a relaxing recorded 'sleep story', red colored night light.
(Sleep meditation we've used is called Bedtime Meditations for Kids - it's an Android app - but there are others out there too).
We also ended up seeing a psychologist (DD refused to go, but us parents went to get advice on how to work with DD and talk to her about her anxiety)
