When you set the page as a posts page, you’re creating an archive page that is likely using a different template than a single post or page would. It’s possible to show the page’s fields on the posts page, but you would need to manipulate the code in the template that’s getting used.
The problem is that when you run the loop on the posts page, you’ll get data for the first post, not the page itself. You could get the info about the page with this:
$query_object = get_queried_object();
And then you can use the page’s ID to grab the fields from it.
