Buy him out or take a loss, whatever you have to do for yourself. He can't make you "stay", that would be slavery :-) Get a lawyer to look at whatever is written ("oral" don't hold up anywhere legally and if you don't want him as a friend or partner, you are under no obligation, things have changed and he's become someone you don't wish to work with so he's broken any "oral" contract himself by changing the conditions you are working under!). Go see a lawyer if you're unsure about what you are obligated for. Everything else is gravy/friendship and if he's a four-legged rear end, then I don't blame you for wanting out. Don't let him browbeat you further.