1) Once the gift deed is executed through a registered gift deed, then you are the absolute owner.
2) Since your father has gifted the property to you and you have accepted the gift, you become the absolute owner per se. Since you have also taken a loan on the house, that is an additional piece of evidence that you have accepted the Gift.
3) Your father cannot revoke the Gift under any circumstances.
4) With reference to your father retains is the right to use the property till his life time.
Right to use the property during the life time of the donor DOES NOT affect the Transfer of Ownership in favour of the Donee by the Donor.
5) You may refer to the CIVIL APPEAL NO. 4195 OF 2008, Renikuntla Rajamma (D) By Lr vs K.Sarwanamma on 17 July, 2014, by supreme court of India. This judgment is applicable to you and should give you confidence in this transaction.
6) The Above judgment is applicable to Gift deed executed by Hindu's, Muslim, Christian etc as Transfer of property Act is uniform code across all religions.
Section 123 of Transfer of Property Act, defines the mode of making a gift and, inter alia, provides that a gift of immovable property must be effected by a registered instrument signed by or on behalf of the donor and attested by at least two witnesses.