How to adjust line height of 2012 and add border between content and sidebar

Hi, don’t mean to keep asking questions but I tried searching a lot of codes but most of them are for twenty-eleven theme and it won’t work on the twenty-twelve child theme I’m using. I have 3 questions.

1) How to adjust and increase the line height of my post content? I tried to use this in my style.css, all the property works except for the :line-height: 10px” value.

body {
font-size: 12px;
font-size: 0.85rem;
font-family: “Arial”, Helvetica, Arial, sans-serif;
text-rendering: optimizeLegibility;
color: #444;
line-height: 20px; }

2) How to add a vertical border right between the content and side bar? I tried using the follow code to add the border next to my content but it sticks right next to it (you can see from my url). How can I better position it so it’s right between both the content and side bar? I’m using this code: (please let me know if it’s placed incorrectly too!)

.site-content{
border-right: 1px solid #333; }

3) Lastly I managed to adjust the widths of the content and sidebar, but the margins between both the content and sidebar is a little wide. Where and how can I reduce this margin? I tried searching a lot but they mostly don’t work. Here’s my margin codes:

.site {
margin: 0 auto;
max-width: 1100px;
max-width: 78.571428571rem;
overflow: hidden;
}

.site-content {
float: left;
width: 68.204166667%;
}

.widget-area {
float: right;
width: 22.841666667%;
}

Many thanks in advance.
This is my url:
https://myfatpocket.com/justjaslin/