After my husband and I obtained Khula, following a year of marriage with regular intimacy, I am currently observing Iddat for 3 months. Post this time, is it necessary to acquire my father's consent for engaging in Mut'ah?
Bismihi ta'ala
From a shar'i perspective, you do not need consent from your father, but I would advice you against engaging in mut'ah, and focus on recovering from the previous relationship, and hopefully finding new marriage.
As a society, one who engages in such things becomes less wanted for marriage, and our Islamic values require that we stay chaste and modest, aiming at building a family.
Also, although shar'i wise, you do not need your father's consent, but ethically, morally and socially, involving family in these things is definitely important.
And Allah knows best