“All of creation” refers to all of God's creation, i.e. the whole world, the whole Earth.
cre·a·tion (krē-ā′shən)
n.
3.
a. The world and all things in it.
b. All creatures or a class of creatures.
4. The divine act by which, according to various religious and philosophical traditions, the world was brought into existence.
Source: Definition of “creation” on thefreedictionary.com
There is an omitted relative pronoun in each of these lines.
It's you, it's you who must go and I who must bide.
It's I who will be here in sunshine or in shadow...
Today omitting the relative pronoun is common only when it stands for the object of the verb in the relative clause:
It's you who I want to see.
But in older English omitting a subject relative was common, and that use survives in dialect and much colloquial use:
You know the people who own the house on the corner?
The author employs this obsolete syntax to lend his song a traditional flavor, just as he uses the obsolete pronoun ye, and the obsolete 'subjunctive' tread in the fourth verse, and sets the song to an old Irish air.
Best Answer
The key to understanding this comes in the article's next two sentences, which I will abridge here:
Of course snake eyes means a bad roll in dice, and zilch is slang for "nothing."
So, the writer is saying:
but saying it in a way that reveals frustration. I imagine her saying it through gritted teeth, or maybe by pounding her fist on the desk with each word:
Putting a period after each word in a short phrase has been gaining traction lately; it's intended to help the reader regard each word emphatically and express emotion. You can read more about it at this ELU question.