Perhaps you can fix this with the No Break style? If you select the word along with the backslash and apply No Break, it should stay together. Yes?

You could do a grep find/change and search for ^+?(.) and replace with $1
That will delete one or more spaces at the beginning of any paragraph.

In what version of InDesign? In CC (maybe CS6 too?) they fixed that… or at least it is much closer. But in earlier versions we had to use a script such as:
https://creativepro.com/custom-zoommagnification-settings-in-indesign.php

I don’t think so. You could go into Presentation Mode (Shift-W), which makes the background black by default, so you can’t see the black line.

I always suggest people use auto numbering instead of page numbering in weird situations like this: https://creativepro.com/use-numbered-lists-instead-of-auto-page-numbering.php

Of course, some stuff simply can’t be done then, such as TOC and indexing and x-refs.

Did you also upgrade your system or computer? On the Mac, especially, the Keyboard settings inside System Preferences often override InDesign’s shortcuts. Fortunately, you can disable those in System Prefs.