What a brilliant interpretation! I have never heard the episode recorded in Gilbert Pinfold identified as delirium tremens, but now that you say it, it sounds absolutely right. I would just add that when Waugh had the aural hallucinations he wasn't just trying to drink less but also to stop taking drugs—chloral, bromide, and those strangely powerful sleeping pills his doctor gave him. So, the voices are a side effect of a brave if ignorant attempt to go cold turkey. I don't know much about it but gather that nowadays, in the drying-out centers tucked politely behind the hedges of remote suburbs, much gentler methods of withdrawal are practiced. Waugh had no idea what he was getting himself into.
What gives his novelization of this particular unreality (as you put it) its disconcerting sense of reality is the familiar ring of the attacks made on Pinfold by his imagined tormentors (the ship's captain, his lesbian sidekick, a BBC host, some aristocratic young toughs and their fathers). They sound remarkably like the slanders Waugh heaped on others throughout his long and distinguished career as England's most vicious man of letters. Pinfold is accused of being "a filthy Jew" whose name was originally Peinfeld, "a sodomite," a shirker from military duty, a newly arrived immigrant, and a rowdy Oxford undergraduate. (Pinfold takes comfort from the mutually exclusive nature of those last two accusations: If his accusers can get caught in a contradiction like that, mightn't they be wrong about other things?) The basic qualities of a Pinfold novel are listed as: "conventionality of plot, falseness of characterization, morbid sentimentality, gross and hackneyed farce alternating with grosser and more hackneyed melodrama, cloying religiosity," and so forth. Waugh unleashes on himself (or at least on his alter ego) the hounds more often trained upon his peers and competitors. The spectacle of Waugh hunting Waugh is disorienting and painful and, as you say, embarrassing. But it also feels like a confession. Waugh is apologizing, in his own weird, perhaps unconscious, way.
You write, "Having been spotted in public conversing with the toast rack, he wants desperately to get a version of this incident on the record that will forestall any attempts to diagnose him as either a drunk or a madman" and call the fight "as pathetic and disheartening as it is moving." One quibble aside—it was a table lamp—I agree with your analysis of his motives, though I'd personally stress the adjective moving. Stannard's biography bolsters your thesis. Immediately upon returning home from his cruise, having consulted a Catholic psychiatrist (whom he leaves out of the novel, in keeping with his pretense that he mastered his illness all by himself), Waugh swears his wife to secrecy. She tells one couple, swears them to secrecy, then shamefacedly admits her indiscretion to her husband. Rather than get upset, he proceeds to regale everyone else he knows with details of the incident. Stannard writes, "Had he been talking about someone else, he might have been accused of malicious gossip." He would probably have justified this on the grounds that the best defense is a good offense, but his obsessive mention of his own humiliation strikes me more as a quixotic attempt to convince himself of his sanity. If he owns up to his madness, then he can't be mad, can he?
Aside from being touched by the genuine anguish on display in this book (which only someone incapable of empathy could ever have mistaken for a black comedy), I couldn't help wondering whether it had had an influence on other books of a similar nature that I've devoured with the same nauseated mixture of sympathy and horror: Philip Roth's Operation Shylock *, William Styron's Darkness Visible, even (to go from the sublime to the strained) Andrew Solomon's TheNoonday Demon. In all these the narrators have breakdowns; they all force us into an uncomfortable intimacy with their all-too-autobiographical inner torments. Styron and Solomon claim to be offering themselves up as salutary examples. Roth, thank God, makes no such pretense. He's out to destroy the credibility of his narrator (named Philip Roth, naturally) in order to mess with our sense of the boundaries between fiction and autobiography. I can't figure out exactly what Waugh was up to in Gilbert Pinfold in the literary sense besides perhaps trying to shock his readers and keep his critics off-balance, but I'm not sure it matters. There's a poignancy and a truth-affect to the book that will outlast all the diagnoses we can offer of it.
One last footnote: Our editor asked me last night what I thought Waugh's legacy was—who the Waughs of today are. That's an incredibly hard question to answer, and I'd like to see you take a stab at it. (Could The Moviegoer, written by fellow convert to Catholicism Walker Percy, be said to be Waughian? It's drier and less farcical than Waugh's novels usually are, but it has the same wry disgust with modern life.) Stannard tells one story about Gilbert Pinfold that suggests another name. It seems that no sooner had Waugh finished the book than he received the proofs of a first novel that was also about a Catholic novelist who hears voices. It was called The Comforters and was by an unknown young Scottish writer named Muriel Spark who was just recovering from a nervous breakdown. Waugh could easily have ignored this book, which after all would compete with his own. Instead he wrote an enthusiastic blurb and a laudatory review, in which he called her novel both more ambitious and more accomplished than his, thereby helping to launch her career as another of England's great satirists. I found both Gilbert Pinfold and that anecdote strangely comforting. It's a relief to be able to say about a writer I can't help but love that though he was a shit, he wasn't a shit through and through.