Hi Steven, let's start with the easy one:
1. Crosshair color / size, I see no reason why this can't be done pretty quickly
2. Scaling of fonts and UI. Lightcube is DPI aware, so if you're Windows DPI setting is 125, 150 or 200% etc. you will see a scaled up version of the application. Are you getting something different, i.e not scaled or poorly scaled? If so what is your DPI setting?
3. Dark mode - a frequently requested feature across my applications. I'm working on it, but it's taking some time and will probably be a couple of months before that is ready.