How change padding around your pages

Try adding these lines to the end of style.css:

#main { padding-top: 0; }

.singular.page .hentry {
    padding: 0;
}

#main is the overall enclosing box for the content below the nav menu. It had some padding at the top that was forcing everything down.

.singular.page .hentry is the box that encloses the post content on a single post page. It too had padding at the top.

For the margin, try adding this to the end of style.css:

.singular #content, .left-sidebar.singular #content {
    margin: 0 5.6%;
}

Sorry, I misread what you wanted to change. I gave you code to change the content margin, and I think what you wanted was to change the title area.

To change that, try adding this:

.singular .entry-header, .singular .entry-content {
   width: 90%;
}