Hello, @TheOne,
Sorry for the delay in response.
1. Your idea is really cool, but unfortunately, this will not work as by choosing the tab or option, the script must have to run which adds the extra amount to the actual amount of the product and that requires extra Customization.
So you can try with Product Addons for Woocommerce plugin: https://wordpress.org/plugins/woo-custom-product-addons/
Hope this helps in achieving what you need.
2. Please read our theme documentation on it here: https://xstore.helpscoutdocs.com/article/132-frequently-bought-together-sales-booster
Regards 8Themes Team.