medication is like hit &miss or trial and error but keep trying ok :)
It might help him and it might now, as drifter0213 said, it's trial and error finding a medication that works. You don't know for sure until you try said medication.
It sounds like your husband need an evaluation with a mental health professional. Is he currently on medication, or has he had medication prescribed in the past? When treating any mental illness, it is always advisable to pair medication intervention with psychotherapy. While I understand your motive with reassuring your husband that his paranoia is unfounded, do not lose sight that his behaviors are delusional and unfounded, and your altering your life and behaviors to accommodate his mental illness is an unnecessary burden to bear alone.
Strattera is chemically similar to an antidepressant, and it's used in ADHD. I'm curious why you ask about Strattera in particular. Has your husband been diagnosed with schizophrenia, or has he never been diagnosed, but you think he might have it? Did a doctor recommend Strattera, or did you hear it worked for someone you know? Is your husband being prescribed medications already? For schizophrenia, Strattera would probably not be the first medication prescribed. Just curious. Take care, and good luck!