Window resizing should not be necessary. The integration package installation instructions explain how to change the width and height parameters of the popup. It says that you must change two lines in the file $CFG->dirroot/lib/editor/htmlarea/dialog.js
Are you sure you did it?
I don't see how installing other filters could affect the behavior of DragMath.
I'm not sure I know exactly which lines the error messages are referring to in your version of Moodle, but I can see approximately where they are. Was there anything unusual about the way you were logged in? For example, were you logged in as Guest? Describe the course you were in and how the HTML editor is being accessed. For example "I was logged in as Teacher and I was creating a Label in a topic block in one of my courses." Then I will try to duplicate the problem.
I apologize for the large font. It started happening and I could not change it. The HTML editor on Moodle.org is mis-behaving today