How do I turn off WordPress errors and just have regular old php errors?

You can add a wp_die_handler filter in your theme’s function.php. You call and execute PHP die() inside the filter, which should end the whole execution. You are then left with a plain error printed on your web page.

add_filter( 'wp_die_handler', function( $message, $title="", $args = array() ) {
   die();
}, 99 );