How should I calculate how much I should ask for emotional distress damages in a malicious prosecution case?

Asked in San Francisco, CA - 9 months

This is a case against a civilian who has sued me and lost over 20 cases/appeals in the last 5 years. The basics he bought the house my dad rented and the judge would not let him kick my dad out and move in; it resulted in 15 years of court cases between the 2 of them. My dad died and we paid him more than expected under the law in hopes it was over. He illegally sued me several times for ridiculas reasons with 0 possible chance of winning. He has lost every case and appeal but keeps suing. How do I determine how much to sue for?