Accessibility questions that are less technical

Hello.  I have a number of questions that are perhaps less technical
than most posts here.  I apologize; they seem too soft SE or latex3's
GitHub list, the tug.org accessibility list does not have substantive
traffic, and the blind-mathematicians mailing list did not accept my
email. I hope folks here don't mind.

I intend to re-make a book of mine to be accessible and I'm struggling
with some things that arose out of some preliminary, practice, work
that I did.

1) At the bottom is an MWE document (I have today's TeX Live and I'm
using LuaLaTeX).  I do not currently have access to Windows so the
NVDA screen reader is not an option.  On Linux, Okular does not read
the math correctly and does not read the alt text or "Black bird." at
all.  Are there better screen reader options?  I'd sure like to do the
highest PDF standard.  At the moment I am developing my docs without
being able to know what is the outcome and it is awkward.   (I have
not tried converting to HTML and using an HTML reader.  I hope to post
the PDF for free download.)

2) Can alt text contain math?  If not, I must write "x times y" and
"the sine function"?

3) Is there any way to influence screen readers outside of textual?
To give a concrete example, I would like to get a pause after
execution of ltx-talk's \frametitle{..} command.  I see that the
package's documentation recommends periods in the title but in the the
typographic tradition that I am used to, headlines don't have periods.
Is this just a matter of hoping that screen readers improve over time?

4) Is there some best practices document that folks could recommend?
For example, googling for guidelines on writing alt text gives many
results but even the most high-profile ones seem to me to be both
vague and contradictory.  For instance, some advocate a character
limit while others recommend extensive description. I confess that I
find it impossible to briefly describe a mathematical graph of the
area under f(x)=sin(x) between x=a and x=b broken into ten Reimann
boxes, particularly without mathematical symbols.  In general, the
advice I have seen online seems more directed to business documents
than to documents for math or science.

5) There is sometimes a tradeoff between what is useful for
visually-impaired users and others.  To again name a concrete example
from ltx-talk, I sometimes show a sequence of graphics as slides
inside of a frame to illustrate changes (say, developing the arc
length as a limit by showing line segments become shorter).  Only the
graphic changes, not the surrounding text.  I understand screen
readers to re-read the entire slide; certainly Okular does.  That's
pretty tedious after five slides.  Does anyone have advice about
working through that?

Thank you,
Jim Hefferon

................ Example document .............

\DocumentMetadata{
  lang        = en,
  pdfstandard = ua-2,
  pdfstandard = a-4f, %or a-4
  tagging=on,
  tagging-setup={math/setup=mathml-SE}
}
\documentclass{article}
\usepackage{unicode-math}
\usepackage{graphicx}
\usepackage{mathtools}

\begin{document}
Red dog.
\begin{equation*}
  \int_{x=0}^1 x^2\,dx=\pi
\end{equation*}
Blue fish.
\begin{center}
  % \includegraphics[alt={Show the integral $\int x^2 dx$ as a
graph.}]{example-image-a}
  \includegraphics[alt={Show the integral as a graph.}]{example-image-a}
\end{center}
Black bird.
\end{document}

-- 
"Does not the Captain seek your advice sir?"
"Not always," said Stephen.