That looks correct to me. Can you give me a sample of the RSS feed you’re trying to import?
Another option is to use the embed by username site setting if you are okay with all posts coming from the same user.
This is unfortunately not possible right now. The embedding tool was originally meant to be “going forward” so it doesn’t have support for dates via embedding. It’s something we could definitely look at adding. (This is the same as issue 3 as far as I can tell).