My guess is that the 7 suspects are all-in-one Red John(like a seven sins ideea). They are all connected. This could explain a lot: "He is mar" = "He is many"; it explains the list being made ahead Jane's thinking; that has many friends and influence; also one step ahead, present almost from the beginning; some of them members of Visualise or all of them, some of them whistle; they all reveal themselves to others(each to whom they had a connection in the past). Maybe Brett is not dead or had to be cut loose.
Think about this ideea in all the situations that you can not explain(in one can be brett, in one can be Kirkland, in one can be Reed and so on...)