Got friend to end his engagement... How do I get him to cheer up?

You wouldn't have been able to talk him out of this unless he already had reservations. She seems hideous, so he probably wouldn't have gone through with it either way. You are now the scape goat, the one he can blame when his family and her family are all hysterical and upset and need someone to curse for this. You're a good friend by putting yourself out there like that.