Hope you’re having a great day 🙂
First of all, I’m sorry for being late for reply, we’re trying to be as responsive as possible, so please accept my apology.
Actually, using Formidable form plugin can give you many features that you can use to get what you need to do. As the problem here is not with the modal box itself but with the form that open links in new pages.
You can download the plugin from here: here
Sorry again for the late reply.