Making the Content Well Wider on a blank "New Page"

Site URL: http://www.davidzamdmer.com

I've got the Lange template and while I've used Project pages thus far, a recent email from Squarespace has me trying a "Blank" page approach. The issue I'm running into immediately is that I can't get the content well to be as wide as it is automatically is with Project pages (100%, or flush with the outer Left and Right margins). I tried injecting code found on these forums within the Settings > Advanced section, but it just runs the text above the header of the site and has no other impact on the design. What is the right code and where should I be placing it in order to affect pages of this kind? Any help would be appreciated. Thank you.

REVISION:

I plugged the below code into the field in Design > Custom CSS, but it affected all pages, including the Project pages.

 #page { max-width: 100%; margin: 140px; padding: 0; }

Any way to have it only affect these "Blank Pages"/"New Pages"?

What is access password?