Showing content from another wordpress installation database in the page template loop?

On your edit2:

If it’s exactly the same, could you add

echo apply_filters('the_content', {$mypost->post_content});

to apply the_content filter to parse the shortcodes?

Also, why not use the multi-site feature of WordPress? If so much is identical, it seems more straightforward to update if your code is not duplicated. And for shared content you could then use get_blog_post(). You can still map to individual domains so you have your url differences.