This plugin automatically sends an email when you publish a post.
Not yet. It's a very simple HTML email being sent using WordPress' email function.
No, you can't have a "Hello Person XYZ" as greeting if that is what you are looking for.
Google's SMTP allows only for 99 emails per day to be sent. So if you added more addresses, it simply won't work. You could create a list or an alias and send your blognewsletter to that address instead.