My guess would be Gale Bertram (I)

Not so much clues, but since Bruno likes numbers and clues.  I took the liberty to assigning numeric values to names.

Now taking the alphabet and give A a value of 6, B 12, C18, etc. (Each letter value increases by 6 until you get to Z which has a value of 156.

Now this is off the wall, but wait...

Everyone says 666 & Red John have a lot in common.  So lets look at the number list I have above.

Mark of Beast = 666
Other Gods = 666
 A End of Times = 666
A President = 666

Lucifer = 444 so take 444/666 you get .666
Red John = 444
Jesus=444 (who does Lucifer try to imitate?)

Grace Van Pelt = 744 (don't know if this is anything or not)
Jay "Red" Roth = 744

Gale Bertram = 612 (what is is middle name?) Gale I. Bertram = 666
Ray Haffner = 612

However if you put first Initial as in G. "Red" Bertram you get 666

I don't think Heller actually went this far in advance to put this type of clue, but you never know.

However when you look that the not for Patrick that says "Dinner is in the oven." you will notice that each of the letter "E" is written differently.

Now go back and look at Bertram's hand writing and notice he has a tendancy to change his letter "E" from time to time.

Now for the final numbers game:

If you put Gale Bertram is Red John you get a value of 1224 since he is two people if you divide by two you get 612!

Having fun with numbers what do you think?