I'm not sure I would reject the 'Secret momoirs' - at least without having read them first. It does rather suggest that Barnett has been rather less than meticulous in his research.
As regards the liking for fires (aversion to draughts!), his doctor is also reported as having warned him about his liking for long, very hot baths, saying that they were 'debilitating'. (Knowing that, and with modern knowledge, we might wonder if certain, er, 'difficulties', were not entirely the fault of Josephine?).
I doubt if Berthier - having had his head rammed into the fireplace - would have described him as cuddly.
N seems to have been an extremely complex character. The dividing line between genius and madness is after all, a fine one.