Funny thing is: This episode didn't really give us new leads.
Partridge wasn't shown, what happened in the room wasn't shown (which means there could be something off), Bertram, despite looking suspicious, wasn't confirmed as Red John...
Maybe everything is a setting for a huge twist on the next episode?
Not really much of a theory, but I've been thinking.
Even though I hope this isn't the case, it might be possible that red john is a psychic.
'He is mar' could be 'He is magic' as well. It could be an unfinished G. If not, it probably is 'he is many', because I don't see how the handwriting would indicate a proper R or a D, in 'he is married' or 'he is mad'.
Just chose Haffner because I like him for being red john, although I think the evidence we have is way too ambiguous for me to be sure it's him or not.