Hello,
1) Check now. We have added some custom styles to child theme style.css to fix the issue.
8) Changes added to Theme Custom CSS and Additional CSS and child theme style.css won’t be removed after any theme update because theme update works with theme files only, unoften – DB fields/tables related to parent theme only, not to WP or child theme.
9) You are welcome. Keep in mind that you can also change the container width in Theme Options > General > Site width if default 1170px is not suitable for you and you prefer wider layout.
10) Yellow pencil works with classes and ids. You won’t lose changes if classes or ids that were used to change something won’t be removed or HTML structure won’t be changed. We work on improvements of theme from time to time and it means that HTML structure changes not always but sometimes. So, you won’t lose your code but I can’t promise that code will be working if something completely changes.
Regards