Suggested answer:
(1) Examples of "nothing to cry about" preceded by it and there:
It's nothing to cry about.
There's nothing to cry about.
(2) We have two different grammatical expressions, one containing referential it and one containing existential there. With referential it we have a situation where it points back to a specific event ("it"), and someone is told not to cry because of that particular event. With existential there, on the other hand, we have a more general statement with no reference to any event in particular. However, in the context there is bound to be something that could trigger tears.
(3) Example of the search string there it was in context:
There it was again upon our left!
There has a locative function in this expression, it is an adverbial (adjunct of place).
It in this context is referential; it refers to "a low moan" in the preceding sentence.
(4) Line 3 provides the following example:
But it's obvious there's no one.
This is an example of anticipatory it, anticipating the real subject "(that) there's no one". The real subject is a Ø that-clause introduced by existential there.
Read about it and there here
Terminology: adverbial, adjunct, anticipatory it, referential it, existential there, that-clause