The following I’ve gotten by viewing this page on the Espied demo site.
@media screen and (min-width: 37.5em) {
.page-content, .entry-content, .entry-summary, .entry-header, .entry-meta {
max-width: 700px;
width: 100% !important;
}
}
The above is more-or-less a blanket change that will affect all pages on your site, portfolio, static pages, blog, category, date archive and tag pages. if this doesn’t work, we will have to wait until the site is live so that I can look at exactly the page(s) you are wanting to widen.
Just for reference, for readability, the golden rule is that lines of text should be around 66 characters maximum (including spaces and punctuation). Longer than that, and the eye can have trouble moving from the end of one line to the beginning of the next. As designed, the text line length is around 80 on Espied when viewed on a desktop monitor, so if you also include text with your Portfolio projects, that is something to keep in mind for your visitors.