Masonry set width?

Ive been trying all night to work out why I cant set a specific width with the Masonry gallery – I have tried everything and unless theres a setting I cant find … it just keeps locking in at a width of 320px, when I need it to set at 500 … so I tried setting my thumbnails to 155, plus 30 buffer … thats just under 500, but no go.

I have to use shortcodes, because for some reason I cant actually access the “insert gallery” selection, as all I get is a white screen and a bunch of errors in the consol .. I have even tried to set the width in the shortcode.

http://www.invurt.com/2013/10/03/snapshots-ero-art-ghost-kitchen-truck/

What am I doing wrong? Why cant I resize my Masonry to be the exact size that I want it to be, with it then being filled with thumbnails?

Have to say, the settings for this new nextgen are far from intuitive … and what is also up with the blank page screen when trying to add a gallery?

Argh. From one frustration to another =/

http://wordpress.org/plugins/nextgen-gallery/