I think that you have every reason to be angry! I definitely would be. You obviously know how to take your meds responsibly. I cannot believe that they would even say that to you. I hate to think of what I would have said if I were in your position...they probably would have kicked me out of the program just for my reaction. But that's besides the point. I think that your honesty in telling them what meds you take, the doctors' letters, your grades/NLN scores, and your work/volunteer history should be more than enough to change the dean's mind. Our nursing school doesn't do drug tests, but I can honestly say that our dean would not kick someone out for this reason. She would probably talk to you to make sure you didn't put yourself or patients at risk...but she would be reasonable about it. Now if someone came to clinical after taking these meds, she would kick them out...but otherwise, nope. If I were you and they kicked me out...I would definitely take legal action. STCC would be paying for me to go to another, more reasonable nursing school.
I'm sorry if I rambled...but I cannot tell you how angry this makes me. I hope that everything works out. Be sure to update on the situation!