The irony of suffering
Mr. Sammler feels that there is a dangerous dramatic irony looming in New York City. The whole community seems perfectly occupied by personal success and winning big in life, for a life of power and wealth. But, Mr. Sammler is a Holocaust survivor, so he sees life for the risks and turmoils that it implies. He feels that those who fall for the American Dream will be extremely surprised by the true gravity suffering.
The irony of family
One should think that Mr. Sammler might support the American passion for the home, but he notices that the American version of family is somewhat consumeristic, and the popular opinion of romance is still consumeristic, he feels. Where Sammler comes from, a family was someone you'd give anything to save, but to no avail. He knows that family eventually involves mourning the dead, and watching as loved ones suffer cruel fates.
The irony of PTSD
To Mr. Sammler, his opinions are rooted in fact, but then again, he also was literally traumatized by his experiences. Then again, Sammler is traumatized by real life, and so he understands instinctually that in some ways, the PTSD serves him (although at that time, PTSD and that sort of mental wellness language was actually not very popular). He knows that while others are distracted by prestige and luxury, he himself has secret knowledge of suffering that keeps him in constant remembrance of death.
