Okay, that's easier to solve. If you edit the rule, you'll see it has a "Send E-mail" action, and that action specifies fields. If you're using the Default Template, those fields are "Event Info" and "Detection Time." There's no field for Detection IP!
You can add one, or make your own template. For example, I created this template in my lab:
You'll notice it has a lot more than 2 fields! Then you can use this template in your Action, and it'll include all the fields you want.
In your rule, you'd follow these steps (I made a video):