In regards to your first question, I would personally recommend not doing this. Just let it go. Doing so will just make you appear even more "disruptive" or however your school chooses to label you. I will also give you some advice, there are a lot of things you can do wrong as a pharmacist and get away with but as someone who is charged with the ethical use and safeguarding of drugs, it is in your best interest to stay far, far away from any sort of illegal drug use.
I'm also a little confused why you would tell the school that you smoke marijuana socially if you only tested positive due to second-hand smoke (that seems to be what you implied above, correct me if I'm wrong).