I’m afraid I don’t have much in the way of good news for you.
1) image description or title does not show
2) the user is presented with arrows and is allowed to browse to images not contained in the post, but ones that are in the same category (or indeed search string)
I apologize, but there is not feature of the theme to alter either of these things.
Something else I’m trying to achieve is to have the thumbnails in post list/grid non-clickable (which can be set) but still retain the option to have an enlarged image show in lightbox on the single post version.
You could possibly just hide the featured image on the single post page via the “Post Options”. Then just insert the image manually at the top of the post. Link it the lightbox and maybe give it the class “pretty” so it has a nice little frame around it.
… but on featured post pages you get two images showing.
And then because you see this happening, you’ll need to use excerpts where ever you’re displaying the posts.