The second best solution is to just reiterate your original timeline and say NO(even if you do it quietly) when anyone tries to change it. If they keep meddling and trying to get you to work off hours, let them lay you off. The important thing to remember is a CEO and execs are helpless. Don't sacrifice yourself to shield them from their own mistakes and incompetence.
If they miss the deadline, they just spin another lie to the customers. To this developer, this work was the most important work of his life. To the ceo, firing him before anything is finished and spinning a lie to customers is just another tuesday.