Yes, WooCommerce is integrated and fully functional in SaasLand. You can build your own store using SaasLand.
Yes, SaasLand is compatible with Gutenberg.
Rogan WordPress theme comes with “Elementor” which is a very advanced, drag-n-drop page builder. For Elementor related issues, you may check their support: https://elementor.com/support/
According to Envato’s licensing, you can use SaasLand or any other theme on only one website. If you want to use it on multiple websites, you must buy multiple licenses.