How much trouble am i in? Caught: attempt to buy marijuana, trafficking...&more?

It is very difficult to know how officials will handle this. It can range from dropping charges (because you cooperated) to whatever the penalty in your area for possession is. You did not say who searched and interrogated you. Was it school officials or police? To be honest it sounds like if this did go to court a lot of the way they handled it could be challenged by a lawyer. If you are generally a good guy and do not make much trouble I think it might be handled in a way that will be ok. That means school punishment. Hope you learned your lesson. Good luck.