I also really love the point about where the apostrophe "S" should go.
By putting the apostrophe before the "S", it implies that the house
has one specific owner, not all of them. Since Nora is the most
notably "doll-like" character, it seems safe to assume that she is the
"doll" in ownership of the house. Though, I agree that you could
arguably call Torvald the main doll, since he is the only one who
remains within the house. I am more inclined to see the house as more
of a metaphoric house than just the physical house. It implies that
Nora, the doll, is trapped within the house (metaphorically, not
physically, since she can and does come and go from it). I am going to
stray a little from the "doll" argument, and just think for a minute
about the significance of the "house" Choosing a house, to me, seems
like a pretty important point as well. A house is normally thought of
as a place of comfort where one can escape and be sheltered and safe.
Also, a house can be entered and left at will. This gives us further
insight into Nora's character because while she does enter and leave
the house, she is still very much sheltered. It implies that it is a
physical choice for her to stay within the house. She has chosen to
remain sheltered, up until the events towards the end of the play. At
that point, she does end up making the decision to leave the "house"
and make her way in the world unaided. I strayed a little bit from the
topic of Doll vs. Doll's, but I think both parts of the title are
significant.