What is the legitimate, Sharia-compliant reaction a man should take towards a woman who assaults him with insults or physical violence, especially if he knows of the judiciary's bias against him?

It is not permissible for a woman to imitate a man, nor for a man to imitate a woman. The Messenger of Allah, peace and blessings be upon him, cursed men who imitate women and women who imitate men.

Insulting a Muslim is a sin and a major transgression that warrants ta'zeer (discretionary punishment). As for slapping and striking the face, the majority of scholars hold that its punishment is ta'zeer. Ibn Qayyim al-Jawziyya, however, held that retaliation (qisas) is obligatory for a slap.

If the judiciary in your country is biased, then you must deal with fools tactfully. If aggression occurs after tactful dealing, then one should consider the situation of the place, those present, and what the questioner might be drawn into.

It is preferable to consult scholars and wise individuals who are familiar with the details of your local circumstances to determine the optimal response.