Not a bad film, but at least three issues
1. If the writing is really of Nobel caliber, he must have won many awards and accolades already. Why throw a fit only now when you're in your in your 70s? What was the trigger?
2. If you've been successfully making everything work and reached your 70s, why screw it all up now? What can she possibly hope to gain by that? It's not believable?
3. The son is desperate for writing feedback. OK, the father doesn't want to give it, but why doesn't the mother at least do so. Even if he would rather hear from the father, she could surely make some astute comments, which ipso facto would be worthwhile to him.
Something nobody else seems to mention here is that Joe's contribution to the writing was not zero. Indeed he seems to be the one who came up with the initial ideas for the books and possibly also the first draft, so when he said they are a writing partnership that seemed the most accurate statement anyone made about the situation. If the film intended anything different than that the filmmakers should have made that clearer.