Act II of A Doll's House

I wonder what is the miracle that Nora is waiting for. I feel like she is going to do something very drastic. I really hope she doesn't have any plans of killing Krogstad. I also wonder if Dr.Rank's love for Nora will somehow cause him to sacrifice himself to save her from her troubles.
A question I have is how did Dr.Rank's lifestyle cause Dr.Rank's tuberculosis in his spine.