The first clause of the first three paragraphs begins with the word "it", as in It all felt so easy. A free translation for it can be Tudo pareceu/parecia tão fácil.
Next, there are five statements about the word it.
I- In the first phrase it was used as dummy object.
II- English clauses which are not imperatives must have a subject. Sometimes we need to use a ‗dummy' or ‗empty' or ‗artificial' subject when there is no subject attached to the verb, and where the real subject is somewhere else in the clause. It and there are the two dummy subjects used in English.
III- It is used in the normal subject position in statements about time, distance, or weather.
IV- In the second clause - It was like this crazy déjà vu – it could be replaced by Shaun.
V- In ―It did not happen four years ago.‖ it is used to refer to a thing previously mentioned or easily identified.