Let's look at each of your sample sentences in turn.
Breaking this down word for word:
eating-thing → food
deliciousness (as a degree or amount)
[copula]: is, are
Putting this together:
Is food [a degree of] deliciousness?
That doesn't make a lot of sense, ...
Let's look at your sentences and explore their meaning.
This says, "Is the food tastiness?" I don't think that's what you want to say.
This could possibly work, but it still sounds a bit off to me. (But, I'm not a native speaker.) What strikes me odd here is the use of the particle が. Had you written it as
No, you cannot use it like this.
です is used after い-adjectives or な-adjectives or nouns, making it polite. The non-polite form would be だ or nothing for な-adj and nouns, or nothing at all for い-adj.
The ましょう construct in question is one of the conjugations of Japanese verbs, namely the volitional form in its polite version. The non-polite volitional form ...
They indeed seem to contradict each other. However, the rules described in the preceding pages should not be taken too literally. The book itself offers the following caveat in p286.
As for the examples you copied from p287, the authors probably needed a few ...
乗る on its own only describes the action of mounting or boarding itself. The "destination" marked by に must be a vehicle (or a boat, a horse, etc), not some geographical location. 東京に乗る or 仕事に乗る does not make sense (although "to ride to Tokyo" is a valid expression in English). 車に乗る does not necessary mean you travel to somewhere; you may ...
If you don’t know whether or not whatever uttered the voice did so in response to the sound, you might say:
If you suspect it did, you might say:
のか in your sentence should be understood along these lines.
In fact, he could have as well said:
In this sentence, のか means that the speaker is guessing at a cause. To translate the sentence, "Perhaps reacting to the sound, I heard a voice." Kind of a gross translation, but essentially the speaker is guessing that the voice they hear is from someone vocalizing in reaction to the referenced sound.