What amount of alimony should I ask for?

I am married to my husband for 6 years. For first 2 years n marriage, I was working after which because of fights between us, I got upset and lost job. I have tried to get back to my career and managed to set up a small freelance business that earns me in range of 10,000 to 30,000 per month. My earning depends on my capacity to deliver. We have a 2 year old son and have now decided to take divorce. We are living in a rented apartment in Mumbai paying 21k rent. My husband gets 1 lakh and 5 thousand of his salary per month. We both are BE and MBA graduates. I am 32 years old and my husband is 34. What would be the fair amount I can ask him? i case of monthly maintenance and in case of lump sum? If I take monthly maintenance and get a job within a few months then can he apply for a revise? I am going to take custody of my child. Will I face any binding on doing job or not in the case? regarding property, he does not own one specifically but his parents own a bungalow in other city. he also has a car loan where he has to pay around 16500 every month. Other than that he has FDs and his parents have also done one FD for me. Grounds of divorce are mental torture that he gives me by being abusive and his affair (the girl didn't say yes but he proposed the girl and if they have intimate relationships or not, I don't know. I have their whatsapp chats for past one year. Will they serve as a solid proof?) I have also registered three complaints against him in police: 1. He hits me after drinking and threatens to kill 2. When society was fighting with me for house, he did not support me 3. I have a doubt that he has an affair and that we do not have any relation for 3 years (after I got pregnant) I think, I have mentioned all considerations that were mentioned on this platform while discussing divorce and alimony matters but is there any other factor that is counted while doing alimony calculations? Please suggest what should be the fair amount that I should ask from him.