Forgive me because I haven't read the entire thread, but pediatric anxiety and depression often present with the symptoms you describe - sleep disturbances, distractibity, and irritability (note depressed kids rarely- I mean very rarely- seem sad, but rather irritable). A screening by a pediatrician is a good idea, but honestly is takes a therapist a good long session (often multiple sessions) to diagnose such problems. 15 minutes with a ped isn't enough to diagnose ADHD, anxiety, or depression.

This might be way off base, but I wanted to mention it.