Hi Ben.
There is a setting that you can find in X > Theme Options > Blog > Content : Full Post Content on Index but it would only display the full content of the posts for index pages like the blog page.
It won’t do the same for the archive and category pages, but you can always do a template override through the child theme.
I can give you some information as a starting point on how to achieve what you are aiming for.
First, you will need to have the child theme installed and activated.
Then login through FTP and go to the following directory: wp-content/themes/x/framework/views/global/ then you should find the _content.php file and copy the file.
Copy the file then go to the following directory: wp-content/themes/x-child/framework/views then create the directory global in the views directory. Place the _content.php file that you copied earlier in the global directory.
Edit the file and you should see the code in the file:
<?php
// =============================================================================
// VIEWS/GLOBAL/_CONTENT.PHP
// -----------------------------------------------------------------------------
// Display of the_excerpt() or the_content() for various entries.
// =============================================================================
$stack = x_get_stack();
$is_full_post_content_blog = is_home() && x_get_option( 'x_blog_enable_full_post_content' ) == '1';
?>
<?php
if ( is_singular() || $is_full_post_content_blog ) :
x_get_view( 'global', '_content', 'the-content' );
if ( $stack == 'renew' ) :
x_get_view( 'renew', '_content', 'post-footer' );
endif;
else :
x_get_view( 'global', '_content', 'the-excerpt' );
endif;
?>
Change the line:
if ( is_singular() || $is_full_post_content_blog ) :
to
if ( is_singular() || $is_full_post_content_blog || is_archive() || is_category() ) :
Hope this helps you get started.
Cheers!