Even though your second marriage was not registered, you have evidence to prove your marriage viz., an invitation card or marriage photographs or any other documentary evidence.
Therefore you first apply for death certificate and then you submit an application to the jurisdictional Tahsildar seeking legal heirship certificate.
Once you get that you can get the properties transferred to your name.
If the Tehsildar is not entertaining your application for legal heirship certificate, you can approach court with a civil suit for declaration and mandatory injunction for declaring your marriage with him as valid on the basis of the documentary evidences available with you and to direct the Tehsildar to issue a legal heriship certificate considering you as the legal heir to your deceased husband.