This is business. You need to tell him just what you did to us:
"he is a talented player but has NO experience directing anything, and he doesn't know how to conduct at all. he admitted that he has no idea how to direct an ensemble, but he said that everyone has to start somewhere and that if i believed in him i would have no problem hiring him as the musical director and giving him the chance to learn on the job."
You must have strong experience. Period. He has none. Period. Maybe he can do some OJT, but until he works up to the point he can fully handle things, the answer is "no". No body likes being told "no", but if he's going to pout over it maybe he needs to take his personal troubles elsewhere. As for you, as an opera singer in a highly competitive business where painful rejection is a way of life, you have to make those painful decisions now if you want to stay in business. It's about learning to lead.
Basically he's staying he should get the job because he sleeps with you. That's pathetic. Tell him he need to listen to what he is saying and think about how he'd feel if he was one of the other people competing for the job or who had career implications riding on the success of the project. If he continues to pout you can explain to him precisely how sexy you find it that he thinks he should get opportunities based on who he is sleeping with rather than what he has accomplished.