I was thinking the same thing when I read the post. It sounds like a tough situation you have on your hands. I also don't want to be blunt or rude but your son is 19 and therefore capable of making his own decision. I understand that you want him to go to school but you shouldn't have to bribe him or cater to his selfish and inconciderate demands. It doesn't sound like he is very appreciative of what you do for him. I say let him skip school and go with your idea that he has to move out and get a job. There is just no reason you should have to take abuse of him saying your crazy or unstable. That is just wrong. He's old enough to take responsibilty and make his own choices right or wrong. I am sorry he is being difficult and treating you in such a disrespectful way.
I'll shut up now!! I hope you can figure out something that is good for both you and your son.
Heidu