If you have cell phone with voice recorder/ if not buy a voice recorder and place it in an appropiate place. Have a conversation with him first ask politely and then tell him that he owes you 15000 dollar (make him agree on that)... then afterward be little rigid saying you yourself want to call the cops. Don't let him know about the record the same day. then next day call him on the phone and tell him that you have given the record to your friend (to protect yourself from physical attack) and you;re gonna hand that to the cops next. then pull your money from his ass. Don't worry about immigration shllt. He can do nothing. trust me.
If that does not work then hand your record to the police they gonna get you your money.A
Also, He does not have any right to talk/ask/blackmail ,whatever,  about your status. you can file a charge against him on that too. Go ahead bro fck his nose!!