Let’s make it easier. I want to disable comments and pingbacks
everywhere in all single posts, custom post types and pages both new
and old.
You could remove comment support for your post types.
remove_post_type_support( 'posttype', 'comments' );
// for each of your post types of course
The same can be done when registering the post type, for types that you create yourself. See the supports argument array. Simpley don’t include comments in the list.