A Doll's House reveals that life can be harsh and even living in a seemingly happy family can be a betrayal of one's own sense of identity.
Torvald Helmer is a fairly typical man of his era and so his character is to be expected and is a fair reflection of the times. He apparently dotes on his wife - his authoritative and demeaning treatment is his interpretation of "love" and ensures that "his little spendthrift" is comfortable - or so he thinks - and his family is representative of what it should be. This is very important to Torvald - the need to be his family's head, protecting his wife from having to make decisions that she's just not equipped to do. His character is similar to many men who are oblivious to the sacrifices of their wives - either then or now! Even Nora is confident of her husband and it is only when he fails to support her that she realises that their marriage has been based on societal norms and not on real love. Torvald's inability to see life outside the strict self-imposed boundaries contributes to the main themes of A Doll's House.
Krogstad behaves in a manner associated with someone who does not trust society. He is painfully aware of his past mistakes and does not trust anyone to understand his best efforts to redeem himself. His character then comes across as somewhat threatening. He is basically misunderstood but unaware of how to communicate better. Krogstad's bitterness is indicative of this type of person, disappointed in his youth when his "love" left him and married for money and who, when he has a chance to change his life ses it being stripped away from him when he is exposed and fired by Torvald.
Dr Rank is a pitiful man, also unable to be the man he wants to be. His respect for Nora is appreciated but his feelings must remain unrequited. He suffers due to his own father's failings and is portrayed here to reveal that, in Ibsen's day, the belief that children's behavior and any shortcomings were the direct failings of the parents. No matter who the person is, he suffers due to his parents' social inadequacies, seemingly unable to rise above them.
Most of Ibsen's audience would have been able to - if honest with themselves - identify with the characters from A Doll's House. It is unlikely that any of the men in the audience would acknowledge that these characters are real life representations but nonetheless, they are. Ibsen
was very concerned with portraying realistic social settings and illustrating a conflict resulting from social pressures
and appearances were everything.