I think the three things the wife is upset about is, of course, the death of her child, her husbands seeming callousness towards the catastrophe, or, at least his inability to express his grief about it, and finally, the utter final loneliness and finality of death itself.
The husband tries, albeit unsuccessfully, to address the first two of his wife's concerns. He tries to console her in her grief, saying, "Let me into your grief", even while he admits, "My words are nearly always an offence, I don't know how to speak of anything so as to please you. But I might be taught". Although he is unable to reach her, he is able to at least address the issues, and makes an attempt to understand.
The last of his wife's complaints is something the husband cannot do anything about, because it concerns the very nature of humankind. The wife laments, "from the time when one is sick to death, one is alone, and he dies more alone...the world's evil". She is expressing the sense that true communication is impossible ("You couldn't care!), and that man is doomed to live life in isolation, a condition that only becomes worse after death.
The poem "Home Burial" takes place on a staircase; the wife is at the landing, looking at a grave, and the husband is at the bottom. It is a poem that relates the strain in their relationship because of their child's death. First of all, the wife is upset that the husband buried the child and showed so little emotion as immediately after he discusses his fence, "One rainy day will rot the best birch fence." The wife is also upset that she cannot seem to talk to her husband about her feelings; perhaps, what she really means is that she cannot communicate her feelings. And of course, lastly, she is upset about the death of the child and the grave which she can see from the landing window.Yet the biggest issue this couple faces is healing, for without communication, neither can get over the child's death, and they appear trapped in their own sorrow. The husband cannot break into her world of mourning.