In general there's a balance to be struck between too few files and too many depending on the complexity of your code, but I can think of a few reasons you might want things to be split out for this project. One example would be to split initializing the mastodon client to its own file, then when you're reading code that uses the client you don't have to think about how the client was initialized.
You're right that it can be confusing when tightly coupled code is split between a bunch of files; to use your example it'd probably be cleaner to write petgrabber.ts as an independent function that returns a result, then have a 'post to mastodon' function that takes generic arguments, and call them both from the main file, taking the results from the petgrabber function, formatting them and passing them to your post to mastodon function.
Cool list! I'd recommend checking out the Chuang Tzu, it's pretty essential to understanding early Taoist thought, at least on par with the Tao Te Ching itself in terms of significance and value and generally a pretty accessible read (I like Burton Watson's translation well enough though I think there are some newer ones out). Also, since you mentioned liking the Tao Te Ching the most, you might want to give the Zen Teaching of Bodhidharma a read (I like the Red Pine translation); it also has a very direct and condensed style (though obviously expounding Zen rather than Taoism).
It is kind of funny you summarize the Dhammapada so negatively given you seem to be using a quote from it as your blog's tagline, but I agree that it probably isn't the most valuable work overall for modern readers (IMO it was mainly valuable as a succinct verse formulation of the Dhamma to aid memorization before the sutras were transmitted in a written form).
Also I'd note that accesstoinsight isn't being updated anymore, you might want to switch over to dhammatalks.org since that's where updated translations and newer content is posted (see here for details: https://www.dhammatalks.org/suttas/ati.html).
I will say that the 'Great White Brotherhood' stuff seems pretty out of step with the rest of your list there, but I probably have some bias against syncretic occulitist religious movements since they seem to have a tendency to wildly distort the sources they draw upon. Like this group which seems to associate Buddhist Nirvana with the Christian kingdom of heaven, which I imagine can only be done by hand-waving away many of the basic teachings of both the Buddha and Jesus (since they're really contradictory on several essential levels).