Just started reading Cunningham's & Harrington's Magical Household and have a couple of question on some details.
Yup, got it. Fun book

I really liked the section on keys.
Why and from where did this belief come? I've heard from someone they should be headed towards North.
No idea, though when I read it I simply assumed that it had to do with the rising/setting of the sun. My understanding of the North/South alignment had to do with the recognition of the earths magnetic polarity and sleeping in alignment with it would be beneficial for the bodys magnetic field.
Oh, I knew about Qi Gong being problematic, but Feng Shui? Any further commentaries?
I have no information on this one.
While 'sechs' really means 'six' I don't see any point calling it 'hex' for being related to witches, 'hex' is Greek for 'six'. The German word 'Hexe' (=witch) is derived from 'hagazussa' meaning 'hedge sitter/rider' and not related to 'sechs'.
This one kind of threw me as well. I'm glad Star clarified the lingustic issue re: mispronunciation/misspelling of Deutsch. I was of the impression that the Dutch in that area were of a Christian persuasion and hence wouldn't be using such symbology in practice. Doesn't the book mention something about the symbols being used on barns?
To me I simply equated the statement to mean the use of particular shapes decoratively such as in quilt patterns and the like. It wouldn't be the first time I've been wrong.
While the book is a treasure of relating "these are the practices we found" it's a little light on "this is why it was done" tending to rely more on "this is what we think it was used for". At least that's my recollection. I'd have to go back to the book for anything more definitive.