We are always happy to help you with our theme.
1. Actually checkout is WooCommerce functionality and you can change it’s code in files located in plugins/woocommerce/templates/checkout if you need. But be careful with the changes since they may be lost after plugin update.
2. You should be able to disable this in your Woocommerce settings. Woocommerce > Settings > Shipping there’s a checkbox to enforce shipping to billing address only.