I think (rarely) it is easiest to correct the theme than to modify 100+ applications.
No offense, it is only my wrong opinion.

That's the right opinion. I ran into this when I was trying to set this up. I stopped when I discovered that every program affected needs a special version. That will completely ruin the updates through the plugin manager unless there is maintenance for two different versions. That is not going to happen and rightfully so. A theme has to work on unchanged applications and only affect the display. It should not depend on what monitor(s) I have. That would mean changing code/settings with every monitor change and for every individual user. Basically I want a dark theme changing the color palette. Not bigger/smaller fonts or icons, only colors. I'm going to look into that but I'm incredibly busy at the moment.

Still, this looks very good so we'll see where it goes. A simple drop-in of a theme file as intended is the best result we can hope for.