Hello Bourke,
Thanks for writing in!
First of all, part of your header section is behind the navbar.

Please go to X > Theme Options > Header > Navbar and set your Navbar Top Height which is 98 pixel, the actual height of your current navbar.
By default, you cannot the Posts page or any of the archive pages even if you use the default WordPress editor. That is because the blog index and all archive page contents will be dynamically generated by WordPress. What you can do is to make use of the Global blocks and insert this block shortcodes in the theme manually. And to do that, you must go to X > Global Blocks and create two new blocks, the one for the header and the other for the footer.

Once you have created the block, since your child theme is set up, please add the following code in your child theme’s functions.php file
// For the header
function custom_blog_header() {
if ( is_home() ) {
echo do_shortcode('[cs_gb id=123]');
}
}
add_action('x_before_view_renew__landmark-header', 'custom_blog_header');
// For the footer
function custom_blog_footer() {
if ( is_home() ) {
echo do_shortcode('[cs_gb id=456]');
}
}
add_action('x_before_colophon_begin', 'custom_blog_footer');
Please make sure that you have added the correct global block shortcodes in the code above.
We would loved to know if this has work for you. Thank you.