One teaspoon of cod liver oil gives 4500 units of vitamin A, and 450 mg of vitamin D. You could give him up to 4 teaspoons a day of it if he isn't takin other vitamin A or vitamin D. It should be taken with meals.

The tryptophan should be taken on an empty stomach to be effective. Melatonin sometimes works short term, but for many people it doesn't help longer term. It should be taken on an empty stomach.