It's weird that he gets all pissy when I"m not available at his whim.
Um, he's the boss. I deal with this by explaining my obligations and letting the boss decide what my priority should be. If this is a non-profit he's likely got a Board of Directors or something like that preoccupying him which would explain the absent mindedness. The lying I can't help with. If it truly intentional and not forgetfulness, I would get out of there.