Hi Rika,
First, I would move the style tag into its own CSS tiddler (you are currently actually generating a <style> tag for EVERY result of your $list filter).
Copy just the internal CSS (not the <style> tags) into a tiddler (any title is fine), and tag it with $:/tags/Stylesheet. When TW refreshes (instantly upon tiddler save), it places all CSS with that tag in the page header.
(There are ways to make the CSS dynamic with wiki-text, but that should be explored later.)
Then, once, you have the List and the CSS in separate tiddlers, you can edit each seperately, and use the browser's Dev Tools to target your CSS updates.
Best,
Joshua F