I really like this idea that Pemberley reflects Darcy's charecter. Reading Ch. 43, I get the sense as Lizzy goes into the grounds then further into the great house,she learns more and more of Mr Darcy. And before his gallery portrait, 'At last it arrested her-and she beheld a striking resemblance of Mr Darcy,with such a smile over the face, as she remembered to have sometimes seen, when he looked at her.' For reasons outlined in your post, it was at this point before the portrait, Lizzy completes her personal journey in the revelation of Darcy's charecter. Within her mind's eye, she now has a picture of his real self. JA tells us 'she fixed his eyes upon herself...' Is Lizzy recalling '...when he looked at her'?