How is the medical and prescription information relevant to your tenancy? If the cease & desist is because you are telling people about the prescription information, I am not surprised the landlord wants you to stop. Is it really a problem if you received some of your landlord's mail at the address? I understand the problem regarding storing the landlord's property, but if that was a problem, why did you renew? You could have moved.
Regarding the security deposit. Did the landlord provide a letter by certified mail within 30 days of your move out where he claimed the deposit? If not, you may be able to sue him in small claims court and have him pay your attorney's fees also.
I provide a free 15 minute telephone consult for security deposit claims and eviction defense. No attorney-client relationship is created by answering questions in this public forum. If you wish to create an attorney-client relationship, you must contact me directly and sign a representation agreement. Answers are provided based on general ideas and an answer specific to your situation would require a review of all documents.