I can answer question 1. To read downloaded fanfiction, or any other pdf/epub, you need a reader app. I personaly use the free version of ReadEra because it's the best I've found in terms of range of file formats, general functionality, and ease of use. I like it enough that I plan to spring the $10 for the paid version eventually. Source: about 1 year ago

Sure thing, a quick search yields Asciimath which seems at least at first glance as huge improvement in the syntax department: http://asciimath.org As for LaTeX in general, Markdown beats it soundly in most aspects. - Source: Hacker News / about 1 year ago

What are the syntax differences to https://asciimath.org? - Source: Hacker News / over 1 year ago

I did some Googling, and thought AsciiMath is the answer (simply because it also contains "Ascii" in the name). Turns out it's a different solution. Source: almost 2 years ago

Math syntax is a bit more challenging, because I'm sure no one wants 12 even if that would make the grammar simpler. Attempts to do this are thin on the ground: as you note, Markdown and other similar tools completely punted on math. AsciiMath is one idea, although not what you want in a full-fledged typesetting language. Source: almost 2 years ago

I like to use asciimath for this, though I realize that it's not as powerful as LaTeX or MathJax. There's a decent Rust port: asciimath-rs. Source: about 2 years ago