Before reply to your query , i would like to mention the followings laws for your knowledge and purpose.
A woman is considered as the “wife” only if her marriage to the man is legally valid.
For Hindus, a legally valid marriage requires that:
-both parties are Hindus,
-the marriage is performed in accordance with customary rites of the parties,
-neither party has a living spouse at the time of marriage,
-neither party is of unsound mind at the time of marriage,
-the male is at least 21 years old,
-the female is at least 18 years old and
-both parties are not related by sapinda or within prohibited degrees of relationships.
Further , the wife who lives separately without sufficient reasons or due to personal mutual agreement cannot claim maintenance.
Wife” includes a divorced woman, but she must not be remarried on the date that she files an application for maintenance.
Since, the court has already declared your marriage as null and void , it means legally she is not your wife .
Further she cannot claim any maintenance from you because she has already lost her status to get the maintenance from you legally.
Surat family court has decided the maintenance petition filed by her in your absence ,ie. ex-parte Order.
You should moved an application for setting aside the said order /judgement with one condonation of delay application.
Once, the said order will set aside , you will have opportunity to furnish the said decree u/s.11 of HMA with the reply of the case filed by her and other her application under section 125(3) will be stayed till the time final disposal of the case.
You cannot approach to High court untill your application rejected by the said lower court.
Probability to get positive relief in your favour is maximum.
So,without any further delay, moved above said application in the same court which has pronounced maintenance judgment in your absence.
Good luck and dont forget to positive Rating.