It doesn’t happen yet, it’s something I’ve added into the next version though.
1. I suggest using the featured image, but if you don’t want to set it in two places, temporarily add some code into the content area and select the “Add to excerpt” option, then delete your content.
This option is hidden due to a bug – it’s the only option there that should be visible when no content is added. Working on a fix for that (not as easy as it sounds).
2. Same as above, you’re looking for that Add to excerpt option.
3. The options hidden when no content is added are done so for a reason, as none of them apply unless content is present (the exception being the add to excerpt bug above).