Dang, That sounds real scary and I do feel for you (I am a white hat hacker), So, I do believe that the person that you have been friends with may have some ties back to the dark-net etc.
However I do not believe that he had managed to hijack your iPhone as all apps inside of an Apple device are sandboxed and require permissions to reach out if that sandbox, permissions which only you can grant. It is a good job that you have malware bytes to stop those scammers however I would recommend covering up sensitive info in the future.
I would recommend ditiching the tile and completely wiping all equipment to factory settings and get in contact with suppliers and support to see if they can do anything. However I do believe that {null} is a system term (That means a term that is used is the Apple devices code) that means a certain system function (A core function, Not an app) has returned 0 output (or null) or is failing to return an output or it is a device bug.
So, To round things up, Wipe all devices regardless of wether they are infected or not, Ditch the tile, And contact support to help you resolve this situation. Oh and also change your phone number too as the person may not have hacked your phone however its a bit too easy to get hold of someone’s phone number if you know how to/whom they may be communicating with. And finally, with that loading app, Just pause the download, delete the app and then wipe your phone, Just in case.
Anyway, Hope this helps and reply if not.
Cheers and Definitely stay safe,
Scientist