The form is not the only place there will be a fixed width.
From the Main select list also go to the Form Elements section, then on each form element, there will be a fixed width and height set.
as for the crashing, that may be caused by a memory leak in Dreamweaver. Dreamweaver can be bad about freeing memory it no longer needs. You may need to Restart the computer to get the memory back, and also delete the users cache: