Post excerpt should be in the data returned if a custom excerpt is entered. If content is not entered in the field then you need to furn get_the_excerpt() when looping over the posts.
To get the featured image you need to do this same way that you would when looping over the posts as well.
WP does not return these fields when getting a post as part of the post data.
If you want them as part of the values that acf returns the you need to create an acf/load_value filter, priority > 10, and in the filter loop over all of the posts and populate these things yourself.
