As for the uninvited person being in your house, you definitely don't have to put up with this. Not sure about the tenancy rights in your state, but if another person has access to the premises (and has been going in without your permission) you should be within your rights to ask for them to change the locks. Definitely get in touch with the tenants advocacy service in your area and see what they have to say about your situation. Find out what your rights are and then have a 'chat' with your father letting him know what your rights are (maybe have a look online and print off some information).