Fractional scaling, OLED brightness and i3 wm

Hello, I’m using the i3 version of manjaro on an asus vivobook M3502Q laptop with OLED monitor. The native resolution is 2880x1620. With the default settings, everything is so tiny that it is impossible to read. If I do fractional scaling:

xrandr --output eDP --scale 0.8x.0.8

then part of my desktop background becomes invisible. This includes the calendar applet that is normally in the top right corner of the screen. Also, the screen becomes dim. I have to first lower the brightness manually with function keys, and the increase it again to maximum. It seems that the above command also changes screen brightness, not just the scale factor. But it is not recognized by the hardware controls (Fn function keys), it still shows 100% brightness. For that reason, first I have to lower the brightness to minimum with function keys, and then increase it again.

Question one: I wonder if there is a way to put this scaling factor into a global config file, and make it the system-level default? Is it possible to also set brightness to 100% after changing the fractional scale?

Question two: how can I fix this issue with the i3 background image and applet positioning? It is possible that this problem will be solved automatically if I put the scaling into a global level config file, but at this moment I don’t know how to try this out.

It would be even better to scale text only, not the whole screen. But I guess that is generally not possible, because it would be application specific.