1) We use default WooCommerce function to show breadcrumbs and it does not depend on our theme but on WC plugin. If you have PHP skills you may try to change breadcrumbs structure. Or contact WPKraken team if you need help with this because custom development is outside the scope of our support. Here is our support policy – https://themeforest.net/page/item_support_policy
2) You need to add the mentioned code in Theme Options > Theme Custom CSS > Global custom CSS area.
3) Sorry, but your question is a bit unclear for me. Please read about Blog page here – https://xstore.helpscoutdocs.com/article/44-blog-page As I can see, you have Blog page already – https://mahsa-watercolor.com/blog/ To add Blog or post to Main menu, go to Appearance > Menus > http://prntscr.com/qh2lm3 http://prntscr.com/qh2loy http://prntscr.com/qh2lrr If this is not what you are looking for, describe the question in more detail, please.