Welcome to BSE. Sorry to hear this happened. I know of no way to reliably get an IP address associated with a wallet. Your best bet is the phone number.
That's a UK phone number. I'm not aware of your laws and cannot suggest a course of action.
If you're in the US, then you could start with consulting a lawyer.
As a default response, inform the authorities or consult a lawyer before informing the authorities. If the amount is large enough and you're in the US, they might be willing/able to do something. The authorities won't step in to try and track this guy for 100 USD of BTC. 100 million USD and you may be able to find someone willing to take an interest.
If there is enough value there, outside of official channels, there are private investigation firms / lawyers who may be willing to work on contingency. The fact that you have a name and phone number is a good thing. Not sure if they're real or not.
My point is, from a technical perspective you've hit a dead end. That wallet has only transacted 1.8 BTC:
If the name/number are real then it would be much easier tracking and taking legal action against the person.