That doesn't change who the content belongs to. It just gives some rights to FB. Any, in fact, without something like "perpetual" and/or "irrevocable" in there,

That doesn't change who the content belongs to. It just gives some rights to FB. Any, in fact, without something like "perpetual" and/or "irrevocable" in there, it doesn't imply that they could keep using it after you deleted it (or that you couldn't revoke a grant of rights.)