I went through the steps as requested and here's what I found.
On the first step, I used the "Simple Contact Form" template and decided I would change the text area in Form Builder to an HTML Editor.
I noticed that when doing this, Form Builder could not create the previews correctly and would give this error:
The end result, though, did work on the page as it should and can be seen here: formBuilder2.php.
On step 2, I was able to create the standalone HTML editor with no problems whatsoever.
That test can be viewed here: htmlEditor.php
With step 3, I had a couple of issues. Just like I did with the first test, I decided I would use the same "Simple Contact Form" template.
Right away, I got this error:
This appeared to be a minor error, because after pressing "OK" twice, it did finally allow me to continue going through the dialog and create the form as I had done before in step 1.
But when I loaded the files, I got an error on the page. Something is "undefined" and causing the error. I don't know exactly what is causing the bug yet, but am poking around.
You can see the result of that page here: formBuilderHTML3.php
If you look in the top left corner, you will see "undefined."
In step 4, the standalone HTML Editor looked and seemed to work great.
You can see that page here: htmlEditor3.php
I will continue to develop and give it some real test work on some actual production stuff I have and will let you know what else I can dig up.
I am really excited about the move to CKEditor and the enhancement of the file management tools.