Hey Dan,
regarding your first question: you can simply leave the main content area blank while in the page editor mode for the pages where you’d like the original template to show – without any text in the content area, the template will only show the grid. Or am I missing the point here?
You’re right, that is not supposed to happen, yet I can see that the screenshot does not correspond to the website link you provided above (http://www.codecape.com/new_site). Have you altered the template in any way and is it still topical? I’ve tested the modified portfolio page on the theme demo, and it seems to be working fine with respect to the page margins.
Sincerely,
Andrii / Satori Studio