Some thoughts..
First, no worries, cynicism is not my thing. This Dean sounds like he is afraid of the confrontation with you, because he probably knows that you are right. He is avoiding you, hoping that you will let it go, but you don't have to. His comment about the dislexia, helped me assume his profile - a condesending Dr (is he a doctor?) who uses denial to cover up for his own imperfections. So when you write another letter to him I would cc: some people. Find out if the university has a human rights officer, you could cc that person on the letter. Try to see who is above him in the school (the head of all deans maybe). Also,, amybe a board that is outside the university, like in the USA there is the "Better business Bureu", that when you threaten s business that you will report them to the BBB, often they start to listen. I don't know what would be the paralel in the country you are in, but there might be something. Hang in there rupio..and I'll ask around for more ideas.