Why doesn't it go like "him and his wife"?

Please take a look at this excerpt from The Catcher in the Rye:

I think I probably woke he and his wife up, because it took them a helluva long time to answer the phone.

This phrase confused me. Why does the author not write "him and his wife", rather than "he and his wife"? Also, I'm slightly confused about his use of "a helluva" - could someone give me other examples of its use? I think I understand what it means, but I'm not sure how to use it in practice.

The speaker is Holden Caufield narrating his life. Holden is the rebellious protagonist of the novel, and if you've read much of the book, you'll know that Holden doesn't get along in school. J. D. Salinger is trying to capture how such a character would sound.

"Helluva" is a phonetic rendition of "hell of a," meaning a remarkable example of something. This may be used in a good way. "That was a helluva party last night" means that the speaker enjoyed last night's celebration. Or it may be used ironically. Secretary of State John Kerry was caught on an open mic saying about an Israeli military operation that resulted in casualties, "That was a helluva pinpoint operation," meaning that it was remarkable as an example of how not to conduct things.

Because the grammar is incorrect.

It should be "him and his wife" as you correctly say.

This is probably an example of hypercorrection. The speaker has been corrected at some time for using 'him' instead of 'he', e.g.

"Him and me did it."

He has misunderstood the grammatical rules, over-generalised and gone to the other extreme.