When you use the Settings>Display GUI to enable fractional scaling, as you have done, the setting for org.gnome.mutter experimental-features is being changed from the default value to "x11-randr-fractional-scaling" (for X11 sessions) immediately. It appears, in your case, the setting is not being changed through the GUI. You may want to try changing the setting via the dconf editor sudo apt install dconf-editor or by running the equivalent gsettings command. The gsettings command is gsettings set org.gnome.mutter experimental-features "['x11-randr-fractional-scaling']"

Since your computer is behaving abnorally via the GUI I would proceed with caution.

Once Fractional Scaling is enabled you may want to try a setting of 1.25 to start with and adjust from there.

You may need to restart your computer for the changes to take effect.

If you want to back out of these changes issue gsettings set org.gnome.mutter experimental-features "[]" in a terminal session.