1), 3) Go to Appearance > Widgets > drag & drop the Product categories widget to Shop widget area. Choose the mentioned options.
2) Go to Pages > edit page > scroll down to 8theme page options. It would not recommend to edit columns width using CSS because we use the global bootstarp classes and it amy cause the future issues with the other elements. You can edit columns width either using the mentioned option or by additional PHP customization if you have PHP skills but use Bootstarp classes for your sidebar and content.
4) You are welcome.
