Father harassing me for half salary ?

We are four children to our parents with three daughters and one son and i am the only son and all my sisters are elder to me. My parents worked hard to full fill our education. As my elder sisters are unemployed even after completion of their education , our family is financially weak until i have completed by B.Tech. After completion of my bachelors degree i have took the responsibility of my family and performed the marriages of my two sisters and cleared the loan taken for my elder sister and also taken care of my parents by providing medical treatments, surgeries and purchased gold ornaments for both of them. But recently my father has been creating lot of disturbances to me due to my love marriage. He was against my love marriage and finally agreed only after taking dowry and land from the girls family. But now he has sent me legal notice claiming that he took 20 lakhs for my education , he himself performed my sisters marriage and i was not providing monthly maintainance since last 6 six years which is absolutely wrong. What will happen if he files a case against me with this false alleagtions and what should i do?