These things he's never been before. He's become embarrassing. My father doesn't fit most of the descriptions for Alzheimer's or dementia. He lives independently with some help from family (we do all yard work, repairs, some house work, taking him to some dr appts) He handles cooking, driving, his finances without issue. But in the last year he's had big personality changes, very rude and demanding to people like servers in restaurants, he compulsively talks to strangers even when it's plain they aren't interested in conversation, he's loud and has a mean streak. All of this is foreign to us. He's always been courteous and kind. It's become harder and harder to be around him, but more so to take him places. Anyone else experienced this?
Of maybe he's just getting older and setting aside some of his old suppressed ways. Being rude and demanding doesn't sound good, though.
http://www.alz.org/dementia/types-of-dementia.asp
Also, I'd pay close attention to the things you think he is able to do. Sometimes they aren't doing as well as they pretend. You might be surprised.
A person can have certain characteristics of dementia, but not the others. It progresses differently in most people. My loved one ran her household seemingly fine for a long time, but she was volatile, unkept, too friendly with strangers and lied a lot. Soon, the other things appeared.
I would get him evaluated medically, to see what is causing it, but I would assume that it is medical and not him being mean on purpose. I would try to be patient and give him extra care and protection.
You might also come right out and ask him what's going on. He may be very concerned about a health problem you know nothing about.
Or your Dad could be angry he is aging, that he can't do the things he use to do. Now other people are doing his yard work, housework, and repairs. I wonder if he would be happier living in a place where he would be around people of his own age group, where he has a lot of common? Has anyone asked him?