Can I allow registered users to comment without being logged in or having to be approved?

Those setting should allow anyone to comment (but they have to enter their name/email). (Side note: I usually uncheck the first two option.).

Perhaps the individual posts have disabled comments? Look down below the post editing area for that checkbox (you might have to enable that area via the ‘screen’ dropdown on the top of the page).

If comments are disabled on an individual post, you shouldn’t see the ‘comment’ area below the post.

It is slightly possible that your theme doesn’t allow comments. Change to one of the default themes to see if the comments area (on a newer post) reappear.

Note that your settings do not allow comments past 60 days, so make sure you are testing on a newer post.