The adage 'happy wife, happy life' could be said to have appeared at least as early as 1903, in the final verse of a choice bit of doggerel titled "The Work and Wages Party", where the parallel and rhyming phrases might as well have been no more than a congeries, rather than expressing causality:
I'm a work and wages party man,
I say that's what I am.
You'll find me true and hearty, man,
For that is what I am.
Now, let's rejoice to end the strife,
With all the kids in clover,
A happy wife, a happy life,
And a jolly good turn over.
Sunderland Daily Echo and Shipping Gazette, 22 October 1903 (paywall)
The working man's song was in the neighborhood of three other articles about labor disputes.
From there, I find no further appearances until the adage shows up in a series of real estate ads in 1958, in Abilene, Texas. Here's the earliest of the series:
ABILENE! HAPPY WIFE!
HEAP O' LIVIN'
1358 Leggett Drive.
2 bedroom, deck, plus every luxury in the book. Come by, take a look, and make an offer.
Abilene Reporter-News (Abilene, Texas), 07 Aug 1958 (paywall)
This is again not necessarily more than a congeries of phrases.
In 1970, the same year the adage is claimed to have appeared as a lyric sung by Thomas Jefferson's wife in "1776; a musical play", it shows up again in a real estate ad, this time in The Morning Call of Allentown, Pennsylvania (01 Nov 1970; paywall).
Sporadic use of the adage as ad-man's fodder is not replaced by frequent use until the late 1990's (1998), when Jeff Allan (aka Jeff Allen) adopts it for the title of a filmed compilation of comedic sketches, skits and social commentary.