On Administrative Dashboard in WP, how do I make column 1 wide enough to display my whole Activities dash let?
A bit of css will do it.
I would suggest to create a new css file in you custom directory like /wp-content/plugins/files/civicrm/my_css/my_stylesheet.css
Navigate to Administer->System Settings->Resource URLs and put your URL to the css file http://yoursite.com/wp-content/plugins/files/civicrm/my_css/my_stylesheet.css

In your css file:

#crm-container .column-0 {
        width: 50% !important; // set the width of the left column to the percentage needed
}
#crm-container .column-1 {
            width: 50% !important; // set the width of the right column
}


Note that between the two columns the percentage must sum 100%

The next style will set the columns to occupy the entire width of your screen 

#crm-container .column {
        float: none !important; // remove floating so the column-0 stays on top of column-1
}

#crm-container .column-0, #crm-container .column-1 {
        width: 100% !important; // set the width of the columns to the cantainer width
        padding: 0 0 25px !important; // reduce bottom padding 
}


You might not need to set the weight with !important but it never worked for my without it, also you might need to clear the cache of your browser.