Noname078:
But I’m by no means an expert. ... Again, this is just some thoughts of mine, it’s definitely not proven in any way, but it might help you to consider these ideas.
No need for modesty; your post was spot on.
To add to your points, FF's stories page is generally a bit trash imo. The search feature is missing some pretty necessary options. What makes it even worse is the monetary aspect of it all. People spamming and clogging up the results pages with stories that you have to pay to read, and by constantly fighting for the spot in "Most Recent" by editing, like, two words in the who piece and calling it a "revision" lol. Not going to outright bash people here for putting their stories behind a paywall, though, since I do it too -- but at least I present readers with the option: either pay 2-3 bucks for a formatted, neatly-presented version of my story on Amazon Book store as an eBook, or read the story for free on FF and Deviant art's yucky layouts lol. It's just fetish fiction after all. Plus, not to be rude or anything, but I'm not going to pretend I don't think there are some examples of fetish fiction that is not written to a standard high enough to deserve being put behind this site's paywall.
In any case, OP; what other users have said already is true. I'm sure your story is engaging, especially if you've spent this much effort writing an almost novel-length piece.
Space the chapters out in such a way that your story spams up the most-recent page. Try and make sure the thumbnail picture for your story is balanced somewhere between classy/interesting and cheaply erotic lol. From what I can see, the pictures you've chosen to use are classy, but they don't tell the average browser that there's anything involving: weight gain, bellies, eroticism, or anything remotely to do with blubbery adipose tissue to begin with. I wish this WASN'T a problem... but it is. People can't help themselves but judge books by their covers -- simply due to there being so much damn content on the web. Human beings aren't meant to be quality-colanders. What I'm trying to say is: add a belly in your story's cover image, somewhere, anywhere, and I'd put a bet on your story getting a higher engagement ratio.
Also, perhaps you could even just outright insert a "note" at the top of the very first chapter asking for readers to comment and like if they enjoy the story. The more comments and likes a story has the more it seems to be promoted and viewed.
I relate completely to your grievances about story engagement on this site. Looking briefly at your two stories, I can already tell you're a talented writer. It's NOT a problem with your craft, I can tell you that much. Honestly it's just this whole site being a bit scummy, a little diseased with bots, and very "lowest-denominator". Same goes for Deviant Art, which is saved only by having a larger userbase and therefore a different nature of engagement.