You can accompany your son to Ranchi 

if son cannot afford  legal fees apply to district legal aid centre for legal assistance 

- Every court has its legal Cell .

- From there your son should approach a free lawyer for contesting the case.

- If, your son will not appear before the court in Ranchi personally or on behalf of any lawyer , then the court will grant ex-parte maintenance in favour of her.

- Your case is very critical , and sympathetic , she will not get a single penny from him .

- Better , take help from the legal cell and represent him through a lawyer and thereby file a detail reply after narrating all the true facts .

- And , also move an application for exemption from personal appearance of your son on the ground of his inability of appearance.

- Dont worry , your son will get relief from the Court.

He needs to appoint lawyer or apply to legal aid in that court for free lawyer.  But if doesn't represent then exparte orders will be passed without your son for maintenance.  He can oppose the maintenance on basis of she being warning well.  But he needs to provide maintenance to his child as per law

You need to inform the court of all the facts and circumstances including the wife's adultery act, plus your son's ailment which has documents of doctors if all can be provided and be submitted to judge , the wife will not get maintenance and as your son is blind, he can apply for transfer of case from ranchi to kolkata, it will a big blow for the wife.more details needed to guide better.

1. In any case, you shall have to contest the matter beforev the Court.

2. You can file a petition beforev the Supreme Court praying for transferring the case to your place since your son is not capable of travelling to Ranchi to contestv the case.

The Indian Constitution has provides for a right to legal aid, under which citizens are entitled to free legal aid by the government. Free legal aid can be sought from the National Legal Services Authority (NALSA), various State Legal Services Authorities or District Legal Services Authorities, which were set up under the Legal Services Authorities Act, 1987.

An application can be made by any person in need of free legal services to the concerned authority or committee by sending in a written form or filling the forms prepared by the authorities, briefly stating the reason for seeking legal aid. The application is available free of charge.

Respected sir... 

As facts mentioned above you must approach the legal aid of that court they will provide you the legal assistance and he will represents you in above mentioned case... And if your son wants to be her then it's ok else you must have to file A divorce petition under section 13-A of HMA that will too make a pressure over her... 

Thank you

See presence in court is required your son can file an application for legal aid before the committee or can appoint a junior to contest the case as the case needs to be contested before the court.

You need to find out an advocate who can raise the question of the the biological father of the girl child since her but his at the time when she was not living with him this question can be raised and the court will order the DNA test in this regard before allowing any maintenance also submit your medical papers of insanity in the court in this regard to prove your points

Request some SC lawyer to file trasfer petition in SC. or appear in court once and submit application informing your inability to appear in court due to mental incapacity.

Child belongs him or not ?

If he's unable to hire a lawyer he can take a lawyer free of cost by approaching district legal services authority.

They provide free legal aid to such destitute litigants.

Let him appear before court and express his inability to provide her maintenance for the reasons he may rely upon.

1. As per the information mentioned in the present query, makes it clear that you have a genuine reason to avoid the visiting to the court, but she would definitely take the benefit of the same if not presented by your son.
2. I would advice you to represent your son through any NGO or legal aid for poor people of your district in the court premises only.
3. In this way, he will not have to be there for each and every hearing, but only when ask by the court of law or at the stage of evidence.
4. Then your son would also be able to contest on the ground of her fault and now demanding money when there is not possibility for your son to afford any court order to pay the maintenance.

Sir

If your son cannot pay the litigation charges due to his income then you can approach legal Aid cell of your district to appoint a lawyer to represent your son.

And you can approach High court of west Bengal and file a transfer petition to transfer the case to your district on grounds of condition of your son. 

Also he can file a counter claim on her for maintenance to him as he is disable to earn a good amount.