Can one perform Umrah after the father refused to fulfill his promise, even though the father is still committing adultery at the age of 55?

A father should fulfill his promise. However, if he does not fulfill it, he is not considered sinful by the majority of scholars, especially if no harm results to the one to whom the promise was made due to its non-fulfillment. A son must respect his father, even if the father engages in forbidden acts. The son should admonish him gently or through an influential person. If the father is capable of performing Hajj and Umrah, the preponderant opinion is that they are obligatory for him, and Hajj and Umrah might be a cause for his repentance.