Changing container size

Definitely. Just copy this rule into your custom CSS plugin:

#footer a:hover {
   color: #FF0000;
}

The value #FF0000 is red. You can use this color picker to choose a color and find out its corresponding hex value.

Add these two rules to your custom CSS:

.entry-content * {
   padding: 0 30px;
}

.entry-content h1,
.entry-content h1 * {
   padding: 0;
}

The first rule adds the padding to the left & right. Adjust the amount (30px) to your liking.

The second rule is to prevent the padding from affecting the heading at the top of each section.

Oops, sorry. Change that first rule to this:

.entry-content > * {
   padding: 0 30px;
}

That is, add the greater than sign (>) before the asterisk.

Hmm, which custom CSS plugin are you using? There are some plugins, unfortunately, which convert special characters (like greater than signs) to an escape code. When I view your custom CSS, I see this:

.entry-content > * {
   padding: 0 30px;
}

The > is the escape character for the greater than sign (>). Or did you copy the rule from the e-mail notification? Don’t do that, but copy the rule from the actual post, because a lot of times e-mail clients will convert special characters to escape sequences as well.

.entry-content {
    border: 5px solid #cccc00;
}

Not sure if #cccc00 is close enough to gold, you’ll have to experiment (change the first four characters as identical pairs of two, like dddd, d4d4 or e2e2). Change the 5px if you want the border width to be narrower or wider.