As you can tell from this topic (and many others), spacing is hot topic and a very personal preference. Hopefully the changes you made work out.
As for the theme custom variables/properties, they are all in the app.css file. Open the developer tools, go to the Sources tab, click on the app.css and copy/paste the entire thing (or parts if it) into a code editor of your choice for easy reference. The properties/variables are also here → CSS variables - Developer Documentation, but I find having the full file on hand easier for quick reference.
Here’s a great guide if you haven’t seen it yet: