Dear Concerned,
a) As 498 A has already been filed follow up with the status of action taken by the I.O in the matter, if nothing has been done write a complaint to the SSP/DSP concerned.
b) Go ahead and file a complaint under domestic violence act against the family of your husband and your husband.
c) You would need to file a written statement in the divorce petition challenging all the allegations made on you and also pray for the relief under the same. you may also choose to file an application under HM 24 in the same case filed by your husband. You may also file a transfer petition in the Supreme Court if the divorce filed by your husband is filed outside your state/place where you are living.
d) You can still file for maintenance under Cr.P.C 125 if there is a huge gap in your earning and your husband's earning.
e) Yes, you may choose to speak with your husband and file for mutual divorce after settlement of finances and terms of separation.
f) Depending on the method of separation you choose, the time may vary from minimum of 6 months to 2-3 years.
Best of Luck... Stay Blessed.