Please find my answers in blue:
Q1) Please tell me can i file DV case from my home city?
A1) Yes. You can file from your home city, however, the allegations would be of your matrimonial city. Hence there are chances that your husband may get the case transferred to his city as per correct jurisdiction.
Q2) can i ask for mantainence after going to my parents home?
A2) Yes. As you mentioned that you are under constant torture from your in-laws, then it is your right to safeguard yourself. Also you are being turned out of your matrimonial home without any of your fault hence you are entitled for Maintenance.
Q3) my last salary was 40,000 per month.If my husband provides evidence that i am capable of earning this much will the court grant me mantainence?
A3) Yes. Maintenance shall be awarded as you are not working at present. However the reason behind you leaving the last job shall be crucial. If you left it on your own, then it your decision and you have bear with its results. However, court is obliged to protect your matrimonial interest and seeing that you were driven out of home for no fault shall entitle you for maintenance.