The only thing I would like to relay is that a Signpost is supposed to traverse more ground. Since you are working on a short it’s not a problem but if you were to encode each Signpost this way for a longer form novel you would end up with 16 1-page chapters. Ideally The Past would last a few chapters in and of itself.
As to your other concern about the order, yes, the Signposts are there in the order presented for a reason and it would be wise to follow that order but as far as the Variations, JBarker wrote a fantastic post that I think will answer you questions: