Zapotec,

>> Image properties dialog should have "Constrain proporsions" on width and height.

If select the image and click  button, in the image dialog, you will have the "Constrain proporsions" .

>> - We would like to add our own text into the preview window, just as we had in CE3.0

    a.  Locate and open CuteSoft_client/CuteEditor/dialogs/InsertImage.Frame.aspx
    b.  Find the following code: 
        <div id="divpreview" style="BACKGROUND-COLOR: white" height="100%" width="100%">
           "add your test here" <img id="img_demo" src="../images/1x1.gif"> "add your test here"
       </div>

>> - We would like to set our own default spacing.

Find the Spacing field in the above dialog, and change the default value to meet your requirements.