Quote 19
HELMER: "Do you suppose I am going to make myself ridiculous before my whole staff, to let people think that I am a man to be swayed by all sorts of outside influence?" (2.113)
The influence that Torvald is referring to here is his wife. He's afraid to seem weak in public.
Quote 20
HELMER: "I hear [Krogstad] is a good worker, too. But I knew him when we were boys. […] this tactless fellow lays no restraint on himself when other people are present. On the contrary, he thinks it gives him the right to adopt a familiar tone with me." (2.117)
Here's the real reason Helmer is firing Krogstad: once again he's worried about his reputation.
Quote 21
HELMER: "I must try and appease [Krogstad] some way or another. The matter must be hushed up at any cost." (3.242)
Krogstad was right when he predicted earlier in the play that Torvald would submit to his demands. The crooked lawyer knows his old friend has always been obsessed with what other people think.