"Racing" thoughts- the inability to stop your thoughts no matter how hard you try is a sign of anxiety. As is the sensitivity to not being able to calm down in the dark.
Your right about the light...it will make him sleep lighter than in complete darkness but since he anxious about I would see if he would accept just a nightlight.
Children are more likely to develop anxiety or depression between 11-16 then any other times in their lives. I would take him to a doctor to be evaluated for both (depression may look agaitated rather than sad).
In the meantime you might want to give him a pill of Benadryl to get him over the hump of getting to sleep.
