I am sorry to hear that you are going through this. You will be able to prevent him from hacking your phone or stalking you if you take some legal action. You must remember that even paranoid people have real fears. Your concerns about schizophrenia since it is doubtful that someone in their 50's would have. the onset of a psychosis. Is there any way that you can use this report to your advantage and sue your employer?
Your brother having a psychotic break does not you susceptible but you may need to take care of yourself and seek help when you feel that you are falling apart. Your stalker needs some firm limit setting and some good boundaries on your part. You should protect yourself from him. .