block always stuck at 195px width

This is caused by the CSS of the module

.block-ddblock{ 
  margin: 0; 
  padding: 0; 
  width: 195px; 
  overflow: hidden;
}

You can override the CSS by copying it to your style.css file of the theme you use and
change the width.

.block-ddblock{
  margin: 0; 
  padding: 0; 
  width: xxxpx; 
  overflow: hidden;
}

In the next version of the Dynamic display block the CSS in totally changed.

Hope this helps for now?

There is a beta version available of the module where this is fixed.