From the last of Sunday’s posts:
I’ve been struggling with exactly that thought though all of tater’s post about the trip. A musical ska-fest sounds like a lot of fun.
So just guess. Recipes are not detailed chemistry; they’re records of earlier guesswork that came out OK. If “one can” of mushrooms is 4 or 6 ounces does. Not. Matter. Maybe you like mushrooms more or less than Aunt Sadie did. If you’re really worried about it, simply use 1-1/4 containers of [whatever] whenever the recipe calls for "1 container of [whatever]. That’ll be close enough to offset cumulative shrinkflation. c.f. 12 oz pound of coffee. Use 1-1/2 containers if you especially enjoy that ingredient.
Her Ladyship cooks by rote recipe, measuring out the 1/8tsp of Spice X into a 2 gallon stockpot of soup. I just pour some of Spice X in until it feels right. When I want to try a new dish I hit the internet, read 5 or 6 recipes for variations on the idea, then pick one that seems best, and make that, but with some adjustments for what I like better, or have on hand, or incorporate a feature from another of those recipes that was also interesting. Her Ladyship downloads a single recipe from one of a very few trusted sources and follows it the absolute letter. An extra 1/4 tsp of e.g. oregano would Totally. Ruin. It.
We do not ever help one another cook. He or She, but not both. Much happier that way. We both enjoy eating each other’s cooking, but how we get there is not compatible. Not at all. 
My bottom line: For those of you who think family recipes must be treated Her Ladyship’s way, you’re waaay overthinking this.
Admittedly baking is much more proportion-dependent than any other sort of cooking. That’s also the sort of recipe where actual measurements are almost always used.
Have you talked with him about this in plain English? What does he say? Do you think he honestly believes it came that way from the dealership, or has he derived that idea because he’s certain he didn’t do it so it had to have been them, or is he simply saving face by blaming the dealer to you while wondering inwardly how the heck that happened? Or knowing exactly how the heck it happened, but not wanting to admit his mistake?
Memory problems are real. And are a bear for both the sufferer and the spouse. But unawareness about, or denial of, the problem make it far far worse.
In my industry we totally accept the fact that forgetting and misremembering occurs continuously. There’s too much going on too fast for it to be otherwise. Humans are fallible. So then we do things to offset that. Like physical reminders for pending tasks, etc. But the big jump is attitudinal. We accept that every thought we have is to some degree tentative and contains the seeds of a mistake. Armed with that “I’m mostly sure” attitude, we’re open to correction from somebody else or from external events as they unfold.
People who carry the attitude “My thinking is always flawless and my memory is exact, perfect, and total” are both objectively wrong about that, and make more uncaught mistakes than people of a more self-questioning mindset.
Changing the habits of a lifetime won’t be easy. But if Hubs can start to recognize what’s happening and work consciously against / around it, I predict you’ll both have an easier time. I sure hope you can talk about this. Good luck!
I hate those days. You really earned your post-work bake with this one.