Red John is a single killer who has evolved into an organizational serial killer, all who have the three dot tatoo, (and others, and even fakes and wanna-be's) .  He started out at the old Visualize ranch, (perhaps Stiles or son), and Visualize is still the backbone of moral support.  Many cops are Visualize church members, and they recruit others throughout the country, giving the organization Red John great knowledge and ability, on short notice, in any location (like Tijuana).  

Timothy Carter was not speaking falsely when he identified himself as Red John.  Red John is many individuals.  Red John cannot be killed, because the idea behind Red John is justified killing according to each members interpretation of justification.  

Theresa Lisbon was a personal target of a Red John because she is the written rule of law, not personalized justice killing, and because the crucifix she wears offends a major Red John.  Jane would be a valuable Red John which is why his recruitment was attempted.