The empty box under restrictions means that the javascript responsible for rendering the list of options has not been executed which means that there may be some sort of javascript conflict on the page. Purge caches, see if that makes it work again.
When this is sorted out, in order to see the activity completion option in the list of restriction options you need to have at least one activity in the course with its activity completion activated.
hth
D = Default
M = More
E = Edit
That was a way to set default target view for the Edit action and More action in the activity level. Didn't work very well and has been dropped in favour of patterns. The long term plan is to create a field type for entry action that would provide UI for setting the entry actions.
The Editon view never fully worked. Its name is compelling, to be sure, which often makes it the first choice. It has been dropped from 2.6 in favour of better ways to achieve the intended effect.
I trust the you use the latest 2.3 version from git under the MOODLE_23_STABLE branch. It is as good as it gets before 2.6.
See this post for a custom view link. In 2.6 onward it is made easier in various ways, so upgrade your moodle as soon as you can.
How about showing a different home page of this kind to each logged in user (personalization)?
The editor opens at 100%. The cols attribute affects only the textarea element underlying the editor but not the editor itself. You need to set the width of the editor container. One simple way is to wrap the field pattern in the template with a div element and set its width to prevent the editor from stretching. (See related post at https://moodle.org/mod/forum/discuss.php?d=267859#p1156487) hth