var x

Can be so
UPDATE wpeix_posts SET post_content = replace(post_content, '[sc name=\"book-consultation-btn\"]', '[sc name=\"book-consultation-btn-new\"]');
or so
UPDATE wpeix_posts SET post_content = replace(post_content, 'book-consultation-btn', 'book-consultation-btn-new');

I can recommend QuickForm. Makes calculators with any math and any design. But it takes a little experience. If you have any questions, create a topic in its support.

Your site needs to be checked. But that doesn’t mean the problem is on it. This may be an extension in your browser that shows ads for being free.

I think the QuickForm plugin is what you need.

Most likely, you will not find a ready-made solution. But your functionality is very simple and is done in one evening. To simplify the work, you can also use any form plugin, for example, it can be QuickForm. This plugin has a special customPhp field. But you will need programming skills.

You have a vulnerability in your code: sql injection. You need to clear the POST data.
$number = (int) $_POST[‘number’];

You also need to connect wp-load.php
require_once( $_SERVER[‘DOCUMENT_ROOT’] . ‘/wp-load.php’ );