I have left out the examples you gave of things you wished you hadn’t done, but they were mistakes that many other young women could have made, nothing at all so terribly wrong, because you didn’t have the experience of dealing with this sort of thing, and because you wanted to be polite. You didn’t want to hurt his feelings. I’ve heard of these situations many times before, and can remember some of my own when I was young. We’re so trained to be polite to those who are older than we are, or are in a position of authority, or of whom we’ve been taught to respect, that we give them too much power by telling them too much about ourselves. And then, when they use it against us, or as an excuse to get personal, we don’t know how to react.
As long as you don’t feel are compromising your safety, and don’t expect that he would actually harm you, I would suggest that you stop your campaign of not talking to him. Practice speaking to him very generally, as you might to any other employee. If he says Good Morning, for example, you say, “Good morning, George. Hi, Cindy, etc.” What he wants from you is a reaction, preferably favorable and flirty, but if he can’t have that, then he will get some kind of thrill just knowing he’s upset you, or embarrassed you, and therefore it means you are thinking about HIM.
Try to speak with him in a tone and a volume that can be heard by other people if he is trying to get personal. “George, that is none of your business, and I don’t care for your personal questions. Please stop it.” If you have to, you can go to your boss, but you may be able to solve this on your own by making sure other people hear what is going on just by the volume of your voice. If he confronts you when you are alone, you need to be absolutely up front with him. Tell him firmly that he is a business associate, and that’s it. Don’t be drawn into a discussion of why your attitude toward him has changed. He surely knows he’s way beyond the usual boundaries. If at any point you feel that you might be in danger, go immediately to your supervisor, if not the police, and explain what’s going on. What it sounds like to me, however, is that he is accustomed to taking advantage of young women and gets his jollies out of trying to find out about your personal life. It’s difficult reacting this way to someone you once confided in, but you don’t have to explain. This man knows exactly what he’s done. The best way to turn him off is not by being either friendly and apologetic or angry, but simply indifferent.