Max width configuration.

Firstly, on removing the category stuff, you can use this CSS

.entry-meta .cat-links {
    display: none;
}

#colophon has 80px of top and bottom padding (above and below your ad). You can adjust that with the following. There is also a max width of 80% set for #colophon.

#colophon {
    padding: 80px 0;
}

On the width, the max width for #main and #masthead is set at 80%, as is #colophon (the footer area) so it matches the other main container elements in your theme. You can use the following CSS and limit everything to a maximum pixel value if you desire.

#main, #masthead, #colophon {
    max-width: 950px;
    padding-left: 20px;
    padding-right: 20px;
}

Hmmm, they have a different set up on the blog. We can dump the category stuff, but it will take the permalink with it.

.cat-list {
    display: none;
}

If you do not want to get rid of the permalink, you will have to make a change to content-single.php and add a new span around the permalink stuff and then add a CSS class to it so that you can target only the category links. If you have not yet done so, I would suggest creating a child theme so that any customizations you make will not be overwritten by a future theme update.

Child Themes
Child Theme creation plugins

You are welcome.