Need help with CSS

Hello everyone,

Here's my fiddle: https://jsfiddle.net/Kiwin/kspLfze5/1/ Thanks for pointing me there!

As you gentle souls can see, I have made some progress compared to my initial CSS. However, Sub1 will align with Category1 only when page size increases. And I'm already seeing a disaster when the second category name becomes twice the length of the first. Most importantly, I want Item6 to be the last of Sub3 so that Item7-9 are listed to the right of Item1-3.  


Thank you.