8051601
The reason I wrote this so fast was because, well, it was already written. I published it on other sites, but I figured a site more specific to its 'fandom' might warrant it more attention.
I have the other stories ready, save for the 5th [volume 4], and a series of stories set between them [untold tales]. But other commitments have detracted me from uploading them, namely an original sci-fi novel I've been toiling away at in publication hopes, and of course, work commitments.
Once I finish the first draft and am only editing the novel, I will be uploading my other volumes. As for Volume 4, its still a work in progress, the only one actually not written entirely yet. So be patient, they will come.
Though your comment about the lack of viewership is a concern I find myself somewhat miffed at myself. I think its because it isn't a smutty romance or it didn't focus on the 'present mane 6 time'.
The latter is something the later volumes fix, they are all set in times when the Mane 6 are around, though events in them have ties to before they were born, though Discord/Tirek/Sombra show that isn't always an issue.
On a minor note, the slightly tedious interface to edit text in documents to upload here makes the chapters a chore to format with appropriate page breaks and such. Oh well, not every website can be perfectly friendly to users...

8058329
Just randomly found the story and I haven't read it yet, but I can't help but think that a large reason you are not getting publicity is that this story is featured in so few groups. Shoving your stories into as many groups as possible greatly improves its chance of being discovered and read by people. While It is not a promise of popularity, I can say that one way or the other, more people will find and read this story. I can't recommend a lot of groups as I haven't read your story yet, but I can give you a few general recommendations.

• The Shameless Self-promotion Bureau
• Struggling Authors
• I Just Want A Comment
• Completed Story Compendium
• Long Fics
• The Underappreciated Story Society
• Long Reads: 10,000 Words
• The Barcast (specifically the, we don't care what goes here, go nuts folder)
• 100,000 Words

Before submitting your story to any group, always make sure you understand and adhere to their rules first.