How can I load the css and jquery explicitly for the login screen

You can load scripts and styles on the login page using the login_enqueue_scripts hook. You can use the same enqueue functions for scripts and styles that you’d use for other pages but they’ll only load on the login page:

function wpse_330353_login_scripts() {
    wp_enqueue_script( 'handle', '//example.com/url/to/script.js' );
    wp_enqueue_style( 'handle', '//example.com/url/to/style.css' );
}
add_action( 'login_enqueue_scripts', 'wpse_330353_login_scripts' );

None of this would be affected by changing the URL of the login page.