Of COURSE he was guilty at the end.
He was doing the identical thing to her he had done to Beaky.
Instead of dying on a trip to her mother's, bag packed and perhaps having discussed suspicions with her mother, they now go home and she tells how he "saved" her!
All of his actions were lies, all along, and we only have his word that he went to the insurance company, when he clearly would have called and that's why they responded by phone with letter to follow. Had he really gone, their call and letter would not have been needed.
The detective's account of Beaky's demise in Paris included some testimony from a French hotel worker with limited English who believed Beaky called his companion (who supplied the lethal glass of brandy) either "Aubeam" or "Allbeam". Remember that Beaky constantly called Johnnie "Old Bean".
And of course he killed his friend for the money, the same way he was setting up his wife from the start. The job and fox wrap for the unnecessary maid was a hint at future plans. When he introduced her to his wife, he seemed insincere saying they'd never met.
In the book he even killed her father.
So at the end, she was placated but going home with a scoundrel, just like any battered wife.