Fantastic guide!!
One note, though: I found it easier to farm everything by saving in the room on the balcony before going down the stairs. That way I could:
Go downstairs, cap the first zombie with the pistol (usually getting a critical)
Take out the 2 zombies with the shotgun
Open the door (puzzle++)
Kill the 2 in the garden
Repeat.
I was getting 5 kills, 1 puzzle, and probably 1 critical per reload, about a minute each. Saved loads of time rather than having to start from the beginning.

Brevity is the soul of wit. ~W.S. / I guess I'm not witty. ~Sasha