Custom Post Type Dashboard Tab not displaying any posts

pre_get_posts doesn’t just run on the frontend, it runs on all post queries, and that includes RSS feeds, XMLRPC, AJAX, REST API, and WP Admin.

You need to check in your pre_get_posts filter and exit early so that it only applies to the places you want it to apply to.

e.g.

if ( is_admin() ) {
    return;
}

Additionally, this code is incorrect:

if ( is_archive('job') ) 

This checks if the main query is a job archive, but it should be checking if $query is a job archive, so it needs to be $query->is_archive( 'job' ).

This is also followed by another bug:

$days = get_field('job_expiry_days', 'option');

If job_expiry_days is not set, then it will be a falsey value, resolving to 0, meaning only posts older than 0 days ago will be found, aka nothing.