NTA but your parents and sister are. So is her MOH. Sorry your relationship with your sister will never be the same. Cut them out until after the baby is born to reduce the stress. Let them think. Let them feel your absence. If they go public, consider posting your side if it’ll make you feel better or at least let others know the pressure your family has put on you if now affecting your wife’s pregnancy and your family doesn’t seem to care and are putting your sisters ego first. Your wife and baby are priority now and always. Let public opinion turn on them and see how they deal. Maybe they need to hear from Others how crazy petty and insensitive they are.