OK! allow me to get to work here! I played this all to many times and have theories of my own. There is one thing I don't agree with and some things I would like to add. I do not agree with you on what the friend is. I think the "man" is hunting him and, as I think your theory of him tracing prey through electronics makes sense, he hears your friend through the phone and thinks you are him, meaning that different things happen depending on the endings you get. Here are those theories:
Bad ending: He comes for you and succeeds in it, but eats you far to fast and before he realizes you are a different person (if he can)
Good ending: your friend gets there and the man tries to go to the door before it gets most likely locked and you find the window he half broke trying to get in.
Final ending: He finds out your friend is somewhere else via him interfering with your phone and goes there. that's it.
Anyway I think that the time loop theory works only because your friend knows you have encountered the man before. Though it does explain why the man stops him on your phone, and in my opinion also gives a good reason for why he would hunt your friend. Ether way your theories are good and the game is great!