What I can make out from the treatment is that your father is having a bipolar disorder, with psychotic features, or a psychotic episode (delusional disorder or schizophreniform illness).
Although in absence of a detailed history I cant point out to the exactness of diagnosis, its more I can say based on the treatment strategy.
The medications given seem good, and most are recent medications and are very good for these conditions.
Also since scanning is normal that rules out any neurological issues.
If the illness has come down significantly one has to maintain medications, and help the person have as much a normal routine as possible.
Basically olanzepine, is a good compound and can be given at a higher dosage unless weight gain is a problem, or the dosage of the other medication, aripiprazole should be raised. The only thing that one can say is that medications are fine, but at lower dosage, and if there is an incomplete response, one can talk to treating psychiatrist to raise the dosage, although the treating psychiatrist is the best judge as he is seeing the patient.