Hi Sarah,

sounds like you have tried almost everything i tried.
If you wanted to go to the chemist you can get a low dose cortisone cream called Dermaid that is for minor skin irritations and itchy rashes.
I used this on Elle when she was 3 months old - was told to by our GP for a similar reason. I know its Cortisone and you might not want to go there but its such a low dose 0.5%. Mind you its not really a long term solution but may help with Zander getting to sleep.
Sorry i cant be more help.