1. If the property belonged to your grandmother and she died intestate then if she died as female Hindu Intestate, ther her legal heirs will get share as per Hindu Succession Act provision of "General rules of succession in case of Female Hindus".
Did the other Legal heirs gave any NOC to your father? If no, but if they will give, then only your father can freely enjoy the occupancy. If yes then ok. If no and other legal heirs want shate then the property will devolve as per General rules of succession in case of Female Hindus.
2.on what basis she is not letting your family enter the house? Do your family have any other shelter? Where they are staying now?
See, the property originally belonged to your grandmother, therefore your father slone cannot sale the property because there was no will from your grandmother.
3.so much has happened so take steps asap.
4. Where there is right, there is remedy. HRC, HMNGO are for all, when there is any infringement if human rights, etc. then one can seek help from them.
5. If you want to move on then take that step after divorce is granted to you and your wife from Court.
6. Firstly try to consult a local Lawyer, if you need legal aid then you can visit any legal aid camp, besides you can also seek help from HMNGOs' lawyers .