is it possible to format the description text so that I can display an unordered list?
ul-tag seems not to work.
https://developers.facebook.com/docs/sharing/reference/feed-dialog/v2.3
Afaik it´s not possible at all to format the feed message in any way, or to include HTML tags.
You can try action links as described in this thread, but i am not sure if they still work with the feed dialog: action links text in facebook post to wall dialog using javascript not working