Does working as an accountant in the accounting department of an opera at a university that hosts performances contradict Islamic law, knowing that I am responsible for a family?

It is not permissible to work in accounts related to opera that organizes forbidden parties, because that involves aiding in sin, and Allah has forbidden cooperation in sin and aggression. However, if you are compelled to do this work and cannot find your essential expenses, then it is permissible for you to work out of necessity until you find another permissible source. And if you abandon the forbidden work seeking Allah's pleasure, Allah will compensate you with something better.