Hi, I'd like to help you with your question.
It sounds like your friend may have OCD, Obsessive Compulsive disorder. OCD is characterized by fear of germs, the need to have things in order, intrusive thoughts that can be violent and spending time repeatedly washing and cleaning yourself. Your friend can have some traits and not others. He may also be just obsessive but not necessarily compulsive.
It also sounds like he has some type of anxiety disorder with panic. Anxiety is related to OCD and often people suffer from both. And he may also have an eating phobia. People sometimes develop a fear of eating, either as a eating disorder such as anorexia, or they fear that their food could make them sick or is poisoned.
Given that your friend is only 105 pounds, he does have some type of eating disorder. Because he is dangerously underweight, he may have numerous physical problems as a result, that could affect his emotional wellbeing. For example, his electrolytes might be so out of balance it is causing him to feel paranoid.
If the paranoia is not due to his weight issue, he may have schizophrenia. There is a family history so his chances are higher to develop the disease.
If he does not have schizophrenia, he may have Paranoid Disorder, NOS. This means that he has traits like Schizophrenia but not enough to be Schizophrenic. The NOS means not otherwise specified, which just says that he does not fit into any other disorder.
Your friend needs help and as soon as possible. He needs a thorough evaluation and medication. Based on just his weight alone he is dangerously ill. If you can get him to check into a psychiatrist inpatient unit that would be ideal. That way, he can get evaluated and on medication right away. And they can try to work with him to increase his weight to see if that alleviates some of his symptoms.
Let me know if I can help in any further,