When the HP/MP are exceeding to the right in the skill menu, then I think that your game window resolution is too small. The MK UICustomizer plugin doesn't control the skill menu. You can buy my skill menu customizer because then you can move around widgets in the skill menu, or you can look for alternative plugins, because the MK one, which is available for free, only focuses on the main menu.
I like your idea to pin the / symbols to force-align them, so it will very likely come in a future update!