In your first post, JY adviced you stopping knock their

door and contact them directly, obviously you did not listen.

Don't knoch their door ever again, it shows you do not know the law and also showes your weakness (you want to settle), which does not help you at all.

Let Lawyer handle it, it will not be an easy one, since sound the tenant is well prepared and he knows the law well.  But that is only thing you can do.  

Follow the law, quite complain, and that is just the lession you have to pay for being a landlord.