I once had a slightly similar situation with a coworker. More trust issues than honesty issues, but anyway. I decided to write him a letter so I would not get too furious to be able to make my point effectively.
Once the letter was done, I read it, and I knew it wouldn't do any good. He would deny, evade, ignore, pretend, and not even really understand what disturbs me. So I let sleeping dogs lie. Turned completely 'ice queen' towards him, polite but cool, and that upset him more than anything else I could do. Of course he didn't dare talk to me directly about this, and I ignored all the hints. Because any discussion won't be worth it. The guy has too different values. I can’t start his reeducation at this stage.
Try to write such a letter. It's a good exercise: it made me feel better, clear-headed, and calmer. It also made me realize that some people just can't understand the enormity of their misdeeds, you can shout till you are blue in the face and show illustrative diagrams – they will just. Not. Get. It.
It's hard not to be able to make your point. But please understand this guy has serious issues, and probably isn't as self-aware as you are. If he could be so dishonest, he isn't likely to suddenly admit openly that he was in the wrong. For all you know, he might delude himself into thinking that since he wasn't calling the times you spent together 'dates' everything he was doing was perfectly ok…