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1) You can use Mailchimp for WordPress plugin to create own form and add it on a page using shortcode http://prntscr.com/mw79n4 Read more http://www.8theme.com/demo/docs/woopress/#1_newsletters
2) Edit etheme_cart_items function (woopress/framework/woo.php) via functions.php of your child theme.
3) Please describe the desired result in more details. You can use such screenshot maker as Lightshot https://prnt.sc/