Hi There,
Thanks for writing in! The layout of an Ethos portfolio post is a 2/3 + 1/3 columns.
The 2/3 on the right is for the featured image while 1/3 is for the content. You can see a sample here: http://theme.co/x/demo/ethos/1/portfolio-item/roman-forum/
Now if you need the content (Envira Gallery) to take the full width, you can add this under Custom > Global CSS in the Customizer.
.single-x-portfolio .entry-featured {display: none;}
.single-x-portfolio .entry-wrap {width: 100%;}
Hope it helps, Cheers!