dont mind me saying. your father in law's pattern seems lik Alzheimer's disease. my grandmother behaved exactly the same way as your father in law. always hungry and always say things lik ppl ill treating her, nobody wants her and everything which are totally untruth and even said my mum wanna kill her!!! last time no one knows she has such disease until one day she admitted hospital for other illness and doc said she has alzheimer disease. they prescribe her some medi to control. after sometime she is better, seldom behave such way. but still, once in awhile she will behaves weirdly. recently also, but not as bad as last time.