And in the books, didn't Holmes finally stop using drugs? What if the drugs were a way to keep his senses from overloading. With Watson around to help center him, this might reduce the need for some of his drug use. (I'm sure Watson would help him wean off the rest.)

Hmmm... you might have something there.

I could see Blair getting ahold of some copies of Watson's writings (I could see Watson's papers being donated to some local library or museum after his death and thus copies might be available for Blair to purchase or read.)