To remove ads you can add these line in scan rules, after all other lines, so
they take higher priority:
-[name].adnxs.com
-[name].amazon-adsystem.com
-[name].google-analytics.com
-[name].uservoice.com

That site is more complicated because it should work with default rules, but
it can't because it uses url which do not get captured by httrack because they
are not with code href, but with code data-url.

One extreme way would be to first download what you can already, then use
notepad++ to search and replace in files then search for "data-url" and
replace via href or something, but that would probably break the website.
Also some mathjax js files could not download for me which breaks website.

My advice is to give up that one and find some book or similar one easier to
download. Also I can't test everything because of lack of time and internet
speed.

You can find some math books on b-ok.cc