Margin changes, buttons underlined when hovered

I moved my site from http://peterchamberlaincann.wordpress.com to http://www.peterchamberlaincann.co.uk a few weeks ago. I’ve made a lot of changes to the theme using a child, but there’s some I can’t figure out how to do:

-The text and images are stuck to the old 520px “margins” on the Portfolio page, and in WP dashboard when I’m editing a post. It displays Portfolio correctly in Safari (http://s3.postimg.org/y9z3bcxqr/wp1.png) but not in Firefox (http://s3.postimg.org/mjl5tz4yb/wp2.png) or Internet Explorer. This is how it looks in the dashboard (http://s3.postimg.org/bmju57i6r/wp3.png).

-I want to put the sidebar back in, but only on the Blog and all the pages related to that. This is the code that will bring the sidebar back I think:

.entry-meta {
    display: inline;
}

.wide {
    float: right;
    width: 520px;
}

.hentry {
    margin: 0 0 40px;
}

-In the Leave a Reply box, the two “Notify me” sentences are positioned in the wrong place, separate from the checkboxes, but I’m not sure where they’re meant to go. http://www.peterchamberlaincann.co.uk/blog/pendulum-rig/

-I think because I extended the main column from 520px to 720px, it doesn’t display correctly on my phone or tablets.

-Remove the underline that appears on the footer buttons when hovered over.