Your request sounds interesting and I'm sure that this is a good idea.
Squiffy I did not know yet. - It reminds me a bit of texinfo or La/TeX and I will try it, good hint, thank you.

I had a similar idea some years ago.
So I came up with the idea of using the LaTeX text-set programming language to create interactive PDFs.
I even programmed my own interpreter (for simple production of interactive PDFs) in this bizarre programming language, but in the meantime my modest programming skills are very rusty.
In some other languages I usually only have only rudimentary knowledge and I lack any knowledge about iOS and Android.
But if I am right, in Android apps the interactivity in PDFs will not really work.
I do not believe that I can help you, but I will be glad to answer further questions.
(For my bumpy English I have to apologize. I used Google Translator to help.)

Good luck in your project!