How to display all custom fields associated with a post type – IN THE ADMIN AREA?

You need an action called manage_$post_type_posts_custom_column. This will allow you to add columns to your custom posts page. To be more precise, you need a filter to generate the column and an action to fill it with content. In your case something like this (untested):

add_filter( 'manage_chimpmunks_posts_columns', 'set_custom_size_column' );
add_action( 'manage_chimpmunks_posts_custom_column' , 'fill_custom_size_column', 10, 2 );

function set_custom_size_column($columns) {
    $columns['size'] = __( 'Size', 'your_text_domain' );
    return $columns;
}

function fill_custom_size_column( $post_id ) {
    $terms = get_the_term_list( $post_id , 'size' , '' , ',' , '' );
    if ( is_string( $terms ) )
         echo $terms;
    else
         echo __( 'No size', 'your_text_domain' );
    }
}