between/among

Perhaps underlying the debate is that familar, false opposition set up between different kinds of fiction, according to which enjoyable novels are held to be somehow slightly lowbrow, and a novel is not considered true literature unless it is a tiny bit dull.

Question,

" Underlying the debate " why is not " the underlying debate " ? Is it because the adverb word " perhaps " in front of " underlying "

Can the word " between " change to " among " ?

Does the word " between " mean " which......lowbrow" and " a novel.........dull" ?

Is that possible in a relative phrase clause to introduce the rest of the clause that a subject is plural and another is singluar ?

for example,

to which enjoyable novels are held to be somehow slightly lowbrow, and a novel is not considered true literature unless it is a tiny bit dull.