In these examples your grammarly plugin is wrong and your grammar book is correct. 'bread and butter' is heard so often it is viewed as one idea and thus requiring a singular verb. Similarly, 'time and tide' requires a singular verb because the two words again represent one concept or saying.

Oo, this is hard. Because while I think "Is bread and butter good for Ted" is correct, I think "Are bread and butter good for Ted" is correct too. The most normal use of [singular to be] + [A and B] in a sentence would be "Is copying and pasting acceptable". Testing Grammarly, it also doesn't recognise the English subjunctive mood either. It's limited to the most normal forms of the English language and so it can't handle the more poetic and situational things. Don't worry too much about it though. [singular to be] + [A and B] is rather obscure in English and I can't think of any clear rules for it.

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This is a reasonable area of debate. The A _ B concept can work in some contexts. It depends on whether the two nouns represent two separate conceptual objects, or are seen as one collective object .... "the hammer and sickle was the symbol of the Soviet Union", for example. Have a look at >>> https://www.quickanddirtytips.com/education/grammar/compound-subjects >>>> https://ell.stackexchange.com/questions/22791/can-every-a-or-b-plus-singular-form-of-verb-be-possible and >>>> https://ell.stackexchange.com/questions/22791/can-every-a-or-b-plus-singular-form-of-verb-be-possible >>>> https://www.phrases.org.uk/meanings/time-and-tide-wait-for-no-one.html