Maintenance and child custody, domestic violence, divorce , adultery

Hi, my husband is having an affair and wants to marry her that's why he deliberately misbehaved with me alongwith his family members. He is also an alchoholist. He abused me verbally and tortured mentally. I am currently at my parental home since nine months. I have a five yr old girl child, who is with me. My old father is taking care of our needs as of now. I want to divorce him on the ground of adultery and want to know what are my legal rights and about my child's custody as well. Even during my stay at in law's place, he never took his responsibilities properly so I was compelled to take up a job to support my child and self needs. His mother also constantly taunted me for dowry as ours was a simple marriage. He lived in a separate room in the same house. Things were unbearable and I was forced to leave his house eventually. Kindly suggest.