by Greg Brume

Solution: HERO'S FORMULA

The shortest path to a winning storyline is the parts numbered:

30-22-41-62-67-8-56-38-77-24-3-52-80-54-35-47

Take the first letter of each part. You'll get "Squares sentences."

Go to each part whose number is a perfect square and take the first letters of each sentence from the body text:

Part 1: UNRE
Part 4: ACHA
Part 9: BLEN
Part 16: UMBE
Part 25: RSEV
Part 36: ERY3
Part 49: 6THL
Part 64: ETTER

This spells out "Unreachable numbers every 36th letter."

There are eight parts of the story that cannot be reached through the regular storyline.
Part 2: TAKE
Part 15: MIDDLE
Part 23: LETTER
Part 33: OF
Part 51: BOLDED
Part 58: FIVE
Part 68: LETTER
Part 76: WORDS

In almost all of the parts, there is at least one five-letter word that's bolded. These words are (row by row):

awFul joInt ceNts trAde saLsa deLis stYle fiFth thInk niNja
jaDed guEss clAim baCon asHen hyPer emAil aaRon acTor neWly
whIte buTts scHmo trAsh moCha abOut stUck ruNny puTty teRry
wrYly faUst kiNky otHer dyIng buDdy toDdy dwEeb faNny voIce
anNoy viTal grEen miXed waTer paSta doOrs luRid laTer viBes
maYbe deCks drOwn soUth diNgy feTid huRry maYor wiTty crAzy
biKes thEft emPty glAss paRty wiTch gaMes grOup leDge liTes
roWdy weEks haNds atTic drYer teSty leEks diVan stErn teNth

The middle letters spell "Finally, find each part with a country unhidden in text. Sort by country. Take part mod twenty-seven."

Within the story there are twelve countries whose names appear in the story. The names are not hidden within other words, but they are not always used to represent the country. Taking each modulo 27 (that is, subtracting 27 as many times as possible) gets the number in parentheses.

Part 35: Australia (8)