First, have a look at the Topic Toc placeholder. This will build a little table of contents inside a topic based on the headings in the topic and potentially save you having to update the list manually as the OS list changes. The interface for customising things isn't the best, but if you play around a bit you should get the idea (and you can post to the forums for more help if you get stuck).
If the Topic Toc placeholder won't work for you, I would recommend not using H2 as the style for your list of links as these are not technically headings. I would recommend using p tags and then the actual headings would be H2 (or H3 if that style suits better). You can apply a class to the p tag to get it looking as you want (although I would recommend making sure the style is distinct from your heading styles.)
For the horizontal line, you could use the Horizontal Line tag. In RH11 you can access this from the menu Insert > HTML > Horizontal Line. If you are in RH2015, I'm unsure where on the ribbon to access it, but if there is an "insert" tab, it's probably on that. As it's an HTML tag, you should be able to style it in your stylesheet, although I've never tried that. I also haven't tried using this in Responsive HTML, so have no idea what it would look like on different devices.
If the horizontal line doesn't work, perhaps you could apply a class to the last item in the list, which adds more padding/margin and a bottom border ?
Hope that helps with ideas.
I appreciate your recommendations and subjective thoughts on usage of the a href and a name conventions for my stying, but that didn't really answer my question.
That said, your mention of a horizontal line gave me the right info to search for how to insert a horizontal line via HTML and the answer is to include an <hr> tag:
<h2>some text here</.h2>
<h2>blah blah blah</h2>
So, thanks for indirectly answering my question :-)