Hey All,
I got a private message to take this one on, so here I am. Feel free to PM me any time with questions!
The extraordinary diary of William Lyon Mackenzie King, prime minister of Canada for over twenty years, revealed that this most bland and circumspect of men was a mystic guided in both public and private life by omens, messages received at séances, and signs from heaven.
(A) that this most bland and circumspect of men was a mystic guided in both public and
ANSWER: No problem here. "Guided" is a past participle opening up a phrase modifying "mystic". The sentence makes the most sense when we leave parallelism for within this modifying phrase, as opposed to trying some kind of parallelism out side of it (i.e. "was a mystic AND also guided...")
(B) that this most bland and circumspect of men was a mystic and also guided both in public as well as
PROBLEM: The parallel should be "both X and Y", not "both X as well as Y". Also, "a mystic" is not parallel to "guided". Also, there's no reason to use "also" there. Just "and" would be okay.
(C) this most bland and circumspect of men was a mystic and that he was guided in both public and
PROBLEM: "was a mystic" is nor parallel to "that he was guided". If you're going to have "that" after the "and", you need to have had another "that" before the first parallel element.
(D) this most bland and circumspect of men was a mystic and that he was guided in both public as well as
PROBLEM: Same as above, with the "As well as" issue from B.
(E) this most bland and circumspect of men to have been a mystic and that he guided himself both in public as well as
PROBLEM: Same as D.
As for the question about "life" versus "lives", I would agree with those who say it really isn't worth agonizing over issues that aren't tested, particularly one-word idiomatic issues. For what it's worth, I think that this construction is awkward but necessary. The point is that he was guided in both his public life and his private life by a certain set of rules. The word "lives" opens the odd possibility of multiple versions of each.
Hope that helps!
-t