So your post has three different questions. Consider making three different posts next time. :-)
AX UI throughout AX will always trigger a field change immediately after leaving a field where the value has been changed. It is like that in AX. I expect the same behavior in Enterprise Portal.
In EP, when you use the lookup and change a value, the "value changed" will be triggered when leaving the changed field only if PostBack is enabled for that specific field. Otherwise, it will only be triggered when you try to save that row.
As for showing the rich text editor in EP, I'm not sure. Perhaps someone else knows. I would recommend creating a specific thread/post for that question. :-)