A complicated scenario, but here is my take:
The side battle cannot be negated and must be resolved first. Once the side battle is over and the surviving characters return from whence they came, then the original battle resumes. Complainers' ongoing ability to negate hero SAs now takes effect to negate Ehud's CtB SA, but King Nadab is gone, so the CtB cannot be undone. The result of the side battle cannot be negated, which means the "cascading negate" cannot take place. Ehud wins the battle and the side battle results remain unchanged.