If you still have to see him regularly I'd avoid asking him questions he can give elabourate answers to - i.e just say hi to him and be very smiley but don't ask him how is or what he has been upto. What sort of situation do you see him in? Work?
I think it's really cruel of him to be rubbing your face in it after he dumped you, it's not like you dumped him and he's saying all this to try and prove how better off he is without you to save face. I know you really cared about him but what does this tell you about the kind of person he is if he can be so unsensitive and well, mean I'd say. You can do better.
All this "i'm so happy" lark, is he really so happy that he has to continually state this? Happy people don't usually go around saying so do they? I think he's just over compensating and really isn't that great.
It sounds like you're having a bit of a pants time at the moment but I promise things will get better. When I broke up with my ex of 3 & a half years it was really **** for about a year and like your situtation my ex moved on almost instantly and seemed to really land on his feet. A year onwards from that my life is great and my ex's seems a bit dull. You need to get a new focus, mine was losing weight and toning up so maybe you could do that and make yourself super gorgeous. Or save up and get a haircut and buy a new wardrobe or something.