Glenn -

for detail. Now I understand your situation. What a huge ugly mess. And yes you should have known better not to send off angry emails to anybody. All kind of communication in angry tone is always treated seriously because of the latest school violence. It doesn't matter if you are a harmless guy who wouldn't hurt a fly or not. They don't know that nor do they care because nobody's going to take a chance. It can jeopardize your future. But I'm glad it didn't come to the point where you can get expelled and reported to the authority.
I just want to clarify for you what can constitute as "Defamation of Character". By law - it obviously means a false statement made about you that resulted in "damage" to plaintiff as in loss of monetary value/profit, employment, etc. In your case - that coordinator's defamation of you resulted in academic difficulty and possibly a loss of college diploma. Do you have a case there? probably. I have to warn you that this kind of defamation suit is notoriously difficult. Most ends in settlement with little result to gain.
You already know that it's really best to proceed this entire situation with cool head. Just employ a clever tactic to make the coordinator and/or director into making incriminating statements and retain all kinds of evidence (email, fax, letter, etc.) to prove your case. Document Document Document Document everything!!!!! With that - it's an easy slam-dunk case.... the most likely outcome is that the university especially at upper senior level would come down hard on the director/coordinator to issue an apology for you and to comply with your requests with no issue. Lawsuit is most likely not needed because it's time-consuming and expensive. You're lucky to have big man on your side like Attorney General.
Be cool. Be professional. and most importantly - Be Firm! Make sure you got the university lawyer and university president know about this situation (which you probably did). Do try to limit your contact with director and coordinator since they're not being cooperative. There's no point in beating around the bush with them. Let the AG/University Prez handles it. I was thoroughly lectured on this as part of my course. It was an eye-opener learning experience for me on how to deal with any kind of situation like this.
Good Luck!