Again he wasn't renting the place, he was just staying for couple of weeks. Actually it was supposed to be couple of days then a week and now another week.
That has nothing to do with it. What if something, like a water pipe, breaks and no one is home? Your aunt has to be able to get in there.
I think you're r****ded and your friend is r****ded. The only ones who sound sane in this story are the dead cousins. And they're dead. What's up with that?
First order of business is to get your key back from this guy. Why would you give the ONLY key to your apartment to a perfect stranger?? I understand that he seems trustworthy, but c'mon man! You don't know this guy! Second of all, you need to enroll him in an English as a Second Language class IMMEDIATELY. He won't even be able to go grocery shopping, let alone find a job, if he can't speak English. Usually these classes are offered all over the city, so just find one near you, and register him. Once he learns the language semi-decently, you can approach the idea of finding him some work.
Doesn't matter. Any landlord should have multiple keys to their rental. Any lease should allow you multiple keys to the rental and that the tenant cannot change locks without your permission and must provide you with keys if you do allow them to change the locks. Granted it's your aunt's business and I personally don't care if she has one set or 100 sets, but for a landlord to not have spare keys is irresponsible. The landlord is ultimately responsible for the rental.
This, it means he had a spiritual guidness or some other b.s. It was the best thing to come up with in such a short notice and when you have a cop, two premedics and a pissed off landlord on top of you.