I like both Your answer & question 🙂
Its not the full point. Say You need changes in functions.php or any other php file, even empty ones 🙂
Custom CSS is fine for small styling changes & test before aprove in Child Theme style.css
Trust me, im not pulling Your leg here. If All Your changes now are in Custom CSS, then its
easy to make Your very own Child Theme style.css Try search forum for help & update.
And Get it right from start. Last one, You only need to read the first post here:
Kim