Is it permissible to work with one's father in his commercial insurance company, knowing that religious edicts (fatwas) prohibit working in this field?

Obeying one's parents is obligatory, unless it involves disobedience to Allah, or causes harm to the child, or is beyond their capacity. Therefore, it is not permissible to work with your father in prohibited commercial insurance, and there is no sin in not obeying him in this matter.