We are sorry to hear about the issues you are getting when trying to get started with X.
You should absolutely be able to use all the bundled plugin with X without needing a standalone license for those plugins. We also provide the support for those bundled plugins provided that they are about the setup and features that are included out of the box in those plugins. There are instances that those plugins have some premium features that are only available for the standalone license, that is when you need to purchase a separate licenses; but, if you just need the basic features of those plugins, you should be able to use them freely.
Cornerstone has several Video and Audio elements:
Would you mind being specific about the inconsistent problems you are having? If you have no experience in website building an not sure how to build a landing page, there are always the demos available which you can import to your site and use them as the baseline for your site:
The video and audio elements mentioned in the previous answer are all HTML5 supported. Perhaps you missed those elements. You can use them instead of using the HTML codes of those elements.
If you want to proceed with the refund, you will have to file the request in ThemeForest since you have purchased X from there and they handle all the payment and refund requests:
Hope this helps.