As a parent of 4, I totally understand your concerns!
Have you tried to check him for food sensitivities? Most of the time, checking for and changing their diet will have a great impact on their health! Food allergy testing comes in different forms, and please don’t have the scratching test done… it only tests for IMMEDIATE food reactions, and puts the child under so much unnecessary pain and stress! Only a knowledgeable and licensed practitioner can recommend the right test for him.
I wouldn’t start him off on such a supplement as 5HTP without first understanding WHY he isn’t sleeping!