With the weather being so awful, it seems that far fewer people will attend this event.

You could use "far" or "much" but none of the other options work.

Much can’t be used with countable nouns, too and very wouldn’t make sense, more would be redundant, and far would be unusual and a bit unnatural, if you ask me. If you want to express that only a small number of people will be in attendance, say The weather being so awful, it seems that few people will attend this event.

I disagree with Aspara. "Much" in this example would be operating as an adverb not an adjective, and therefore could be used since it precedes "fewer" not the countable noun "people." Although I still prefer far, again operating as an adverb not an adjective. Example, "Far fewer will attend." "I need far more time than I thought."

Also, the example you provided is a statement that few

KJinCali79"Much" in this example would be operating as an adverb not an adjective, and therefore could be used

Then would you say much more apples is correct?