Add those when .dialog-ready event gets triggered.

Yes You can use Asset APIhttps://helpx.adobe.com/experience-manager/6-3/sites/developing/using/reference-materials/javadoc/com/day/cq/dam/commons/util/AssetReferenceSearch.html

You should be able to use ACS API for Creating Profileshttps://docs.campaign.adobe.com/doc/standard/en/api/ACS_API.html#creating-profiles

Form component are designed to keeps forms specific use case which cannot be directly served by general component,Yes, you can use these components and also I would recommend you to look at the form components provided by Core Component libraryhttps://docs.adobe.com/content/help/en/experience-manage...

Make sure to deploy your component code to publish

Two main reasons I have see so far:1.  Incorrect Java version2. User does not have appropriate access to the file sytem where AEM is running.

1. Create the the HTML with <a> and <img> tag for your button2. Create component using that HTML3. Use the component in base template.Above is just  one of the approach, there can be many more.

I am not clear on what you need to locate in file system?

You don't need it.I assume you want to look the content of DAM and as long as server is running, you can navigate tohttp://[HOST]:[PORT]/assets.html/content/dam You may need root access if aem server itself is not running to start it.

You can update the header HTML to add a hyperlink to facebook page. Hardcode the link or take it as a input from dialog. Either way you need to update header HTML for a hyperlink tag