The irony of the wayward mother
The ironic mother is a problem for Jack, because mothers are supposed to teach a person how to correctly perceive themselves. One of the hardest goals of parenting is to raise children who are willing and able to strive for themselves, which Jack starts to do, but instead, he self-sabotages. Why? Because he knows there is an ironic power inversion in his relationship to his mother, and his psyche wants it resolved before he gets too far ahead of himself.
The irony of aggressive men
Why would any man walk into a relationship with a little boy, the son of a prospective wife, by the way, and carry a posture of dominance and aggression? Only a man who has no experience with children would do that. Such behavior is not tolerated in the public sphere, so why does Dwight think it is alright to treat his would-be step-son with contempt? The irony is that Dwight is very weak, and he is paranoid, and something about the scrutiny of the boy's wise and serpentine personality made Dwight feel permanently threatened.
The irony of misperceived reality
The irony of reality is that we are interpreting it in our minds for ourselves, every second of every day. So for Jack, this irony meant that his reality was literally worse and darker than it needed to be, because he self-imposed rules about how he was and wasn't supposed to relate to his mother. He wants for her to save him and rescue him, so he fails to see when he has the option to be at peace. He wants the drama because he knows there are problems to be fixed, but it's hard for him to care about anyone's suffering but his own.
The irony of art and calling
The irony of Jack's experience of art was that back then, he didn't even use his real name, and he equivocated lying with writing. He is abusive and self-destructive, and his long-suffered experience of injustice has made him unable to make art about anything other than his own problems, from the position of a victim. The calling he feels is therefore ironic, because instead of using art as a tool for his own purposes, he might one day feel the other way around.
The irony of Vietnam
Vietnam doesn't actually need to be a symbol, since clearly it refers to itself and to the nature of war. But the synchronicity of Toby's experience is undeniably ironic. It is as if fate itself has lifted him from one story and set him into another one. He feels Vietnam is not what he needs, but then again, was that a war anyone needed? The war comes at a time in his life when he is decidedly confused about existence, though, so whatever crisis he has left will be taken care of in a new adventure. There is literally a sequel to that very effect.
