I think the first two stanzas are fine. My gut is that the final would pack real punch if it were a single line declarative statement. The issue I have is I'm not sure of who the target of the assault is. If the boy, then the mother's absorption is an awkward fit. If the mother, than I don't see how the maternal instincts have failed.
I suspect it's the boy from stanza's 1 and 3, the mother's blankness to the abuse of her child is a crazy, but identifiable and real response. If this is the case I think the word, "absorption" needs to go and be replaced something to better indicate passive and defensive neglect.
I of course could be misreading your intent completely.
Marc