Custom font scaling of interface does not match the font sizes of the hud and only effects the PDA interface.
Alsot custom font scaling for interface does not increase the font size of text chat while not in the PDA interface. For example while in Hud view or pilot mode the text chat and all other fonts do not match the increased size of the custom font scaling.

F5 seems to adjust everything including text chat and fonts in the hud but I'm not sure that is intended to increase the fonts as well.

Additionally, with targetless installed, F5 crashes the game with multiple lua errors. Crashes to desktop.
I'll report that to the targetless forum page.

Do you mean the Manual Font Scaling Interface setting? It looks like all of my font sizes are changing when I change that setting.

The F5 HUD scaling is supposed to change the font size as well.

Are you trying to make the text larger or smaller? There's a minimum font size that you could be hitting if you are trying to make the text smaller.