How to stop uncle from damaging my reputation ?

hi sir, i and my uncle have a deal that he will help me in education , i have to marry his daughter.He spend only 200000 for my education.as my engineering completed and got small job and married his daughter.but he did not give anything for me as a gift(no money no property).but after marriage he is saying he spent around 1800000 lacs for study and marriage of mine.he forcing me to pay back.he is damaging my reputation like because of me he was in bad financial position.he is auto driver.i am a poor student ,no father , only mother.we tried so many times tried to convey him as we are not responsible for that.but he is not listening he is saying untruths . my wife (hisown daughter) also requested but he is not even caring for her life also.we are mentally and financially suffering because of him and i have two kids (2 years),my mother is daily labour, i works in private job.what rights my wife have to take against him?or what rights i have against him to take this into leagal. pls help