The World According to Bensenhaver is Garp's most autobiographical work. This also means that it is the most therapeutic to write—and, at the time, Garp really needs it.
It's easy to see the parallels between Bensenhaver and Garp's own life. Helen, like Hope, is the victim of a rape, although the circumstances differ dramatically. And Garp, like Dorsey, is more concerned with his wife's infidelity than comforting her through the traumatic experience she's just experienced.
Luckily, Garp manages to make their family "whole again" (14.28) by letting go of his anger and guilt. Dorsey, on the other hand, never manages to get his rage under control and ends up dying at the hands of his own paranoia.
This is representative of Garp killing off the person he used to be—the man furious at his wife for an affair after having plenty himself. He still has a lot of growing to do, but The World According to Bensenhaver is a good start.