Hello,
1) He can file a complaint with the police locally against the son about the harassment. He being a senior citizen the police will take cognizance of the offence and take appropriate action.
2) Your father being a dependent without any income of his own can file a petition in the court seeking maintenance from his son who has sufficient means.
3) There is a legal Aid Cell attached to every court. If your father approaches the local court he will be guided to get an advocate free of cost for handling his case.
4) Here is a list of Old Age Home in Kolkata KOLKATA
Nabadiganta
29 Banerjeepara Road, Sarsuna, Kolkata-700061
Women Coordinating Council
5/1 Red Cross Place, Kolkata-700026
All Bengal Womens Union Home
89 Elliot Road, Kolkata-700016
Ramkrishna Satyanabda Ashram
46/2 Desh Bandhu Road, Kolkata-700032
Janasiksha Prochar Kendra
57-B, College Street, Kolkata-700073