> How can I make the cursor in Pages visible? It seems to be a one-pixel-wide yellow line on a white background.
The cursor honors the System Settings -> Appearance -> Theme settings.
The default settings cause the cursor to show in yellow, but you can choose a different theme color and Pages will adjust accordingly. You can't change the shape/size of the cursor, but maybe the color is sufficient.
> Or, how can I make Pages have a White-on-black format?
Pages is designed to replicate the printed document... which is most often black text on a white page. If you want something different you need to tell it so.
For example, for White-on-black, use Inspector -> Section -> Background to set your page color to Black:

then change your Styles to set your text to White rather than Black

> Similarly, how can I make the formatting indicators (e.g., page break, tab, return, etc) visible?
Via the View -> Show Invisibles menu item.
> And how can I make the rulers useful?
That's too vague a question to be able to answer. What are you trying to do with the ruler that you can't seem to manage?
> Migrating from Word has so far been a nightmare...
Pages is not a Word clone.
Word has many features, knobs, buttons, polish, and idiosyncrasies built up over 40 years, primarily catering to the professional user. Pages is more refined geared more towards home/enthusiast/casual uses, although clearly there's a lot of cross-over.
Either way, switching apps is going to incur some level of relearning, and muscle memory can be a hard thing to overcome.
If your goal is to stick with the Word-style of doing things, and if Pages isn't cutting it for what you need to do, then consider alternatives such as LibreOffice which is designed to be closer to Word.