Financial responsibility of child

YOu should try wearing bigger dark glasses which will darken the truth entirely.  When you aer liiving together you cannot file maintenance on wife.  Your son can file a maintenance case on you both through a guardian in court through a advocate.

He can claim maintenance under sec 125 crpc from both of you.  For that he has to shift himself from your place to guardians place.  Now guardian can be grandmom and grand dad.

They can later apply for guardianship and GW act citing you both are spoiling kids life by fighting daily.  Like that you can get your wife to pay money towards childs expenses.

As far as she staying with you without paying you any rent, that comes under section of INDIAN WIFE rules.  Until the day you are alive you will have to pay alimony to her even if she stays with you or stays away from you.  But in case you both get divorced and she remarries you need not pay alimony to her.

But making her pay money through law can be done, to tell all that I will take fees. Free service till here only.