Episode 7 is the great red dragon; from revelations and the paintings by William Blake "the great red dragon" has seven heads. As there are seven names on Jane's list. they could all be Red John!

Jared Renfrew could have been writing "He Is Many".

There are also many aspects of poem "the tyger" that are allegorous with the red john story:

"what immortal hand or eye could frame thy fearful symmetry"
2 sides of one religion with visualise as the eye and red john, the hand

"on what wings dare he aspire"
the winged V symbol?

"what dread hand? & what dread feet"
the painting of nails using the victims blood

"what the hammer? what the chain..."
Roy Tagliaferro - a blacksmith or metal worker

"did he smile his work to see?"
the smiley is always painted so as, to see the ritualistically butchered victim.

some of these are a bit thin, but the Blake theme suggests there must be more to it than Red John likes this poem.