Hi, just got finished with the game and I've got somethings to say.
I'll state upfront that the ending is not a bad one by itself, but it does not belong in this game. If I had to try and summarize it with an analogy then it's not dissimilar to putting a hot fudge sundae in a hamburger. Both are good, definitely don't belong together though.
The game is very clearly advertised as a mind control/alteration trainer and holds true all the way until the end. Maybe some could read some foreshadowing here and there about the ending to come, but it's not anywhere enough and doesn't set the player up for the ending they get.
I could think of so many ways to fix this, the low hanging fruit is telling you to just change the ending completely but I know you've already put so much work into this one and I don't necessarily think you have to in order to make it work. You could try dropping some heavier hints about the ture nature of the bell, maybe even make a slight meta-game within the game to solve as you train the wife.
Another idea is having multiple major endings. I could see several different endings based on how you train the wife and maybe adding new items. An ending where the wife turns out to be very susceptible to Pavlov training and is actually being trained despite the ruse, maybe the husband could find out earlier about her ploy and uses the knowledge to his advantage in some way, or even perhaps another twist that the bell was magical after all somehow and the husband now realizes he has REAL power. I could spit out more but they're all just suggestions off the top of my head as I write this.
TL'DR Good game, well-executed but a dissatisfying ending.