Thank you for sharing the template you are using! The storyboard template uses shapes to create the outline. You can confirm this by selecting the shape and viewing the 
(shapes) option on the object toolbar. This is why you are hitting the 2,000-character limit.
I recommend placing a text box over the shape to retain the square border provided in the template or replacing the shape with a text box. This way, you can leverage the increased character allotment.
We will look to update this template to make it more user-friendly. I can understand how you easily hit the character limit the way it is currently structured.