Possible to only highlight the first heading on-screen?

Hullo! I was wondering if it was possible to prevent the plugin from highlighting multiple sections at once if two or more headings are simultaneously on-screen? I would prefer just the first (top) section on-screen to be highlighted.

Also, is it possible to adjust the offset by which elements are judged off-screen? I’ve made it so that the links scroll up by 100 pixels to account for my site’s header, but this means that if I click on a link, it scrolls to the right place but the previous heading is highlighted as technically the top of the screen is within that section.

Finally, it would be cool to be able to use indentation – is there a specific CSS class or ID that nested headings get, so that I can indent these entries in the table of contents?

Thank you, and apologies for three questions!

The page I need help with: [log in to see the link]