Please try the latest development version from:
regularlabs.com/development-releases

To add a class to the field-value, you need to use the Render Class in the field settings, or to override that, use render_class="..." in the data tag.

The 'intro-' and 'fulltext-' prefixes are reserved for the core images. So Articles Anywhere assumes you are trying to get data from those.

I recommend you change the alias of your media field to something else, like 'blog-image'.

That depends on what class you want to set. Check the field edit form to see the available fields you can set. Use the element inspector to see what the field name is.