What can I do when receiving threatening emails from bod President?

It depends on the nature of the threats. If they are physical threats you should consult a local attorney about possibly getting an injunction. If the threats are non-physical there may not be anything you can do, but you should still consult with a lawyer to make certain. Board members are protected from personal lawsuits for breach of fiduciary duty by the "Business Judgment Rule," which basically says the board members cannot be sued for their mistakes or stupidity. A lawyer would need to read them to determine if it goes beyond that.