Umm, it's not a matter of it being too spicy..
I say that you have to use a true tablespoon, not just a spoon out of your silverware drawer.. to keep it consistant.
A heaping tablespoon is appx. 1.5tbsp.
Anyway, cinnamon doesen't take well to being hydrated in the powder form. It's one of those powders that will just sit at the bottom or top of your drink.. when you poke and prod it with your mixing utensil, you'll just uncover more dry powder...
You wouldn't be able to eat a tablespoon full of any such thing.