Hello Khuram

As you are over 21 and not dependent in your father for health reasons, ( correct me if I am wrong ), you cannot apply for a residence card as the relative of an EU citizen. Family Settlement option is not viable either unless your father is originally Spanish. If he got his Spanish Nationality based on long term residency, the Family settlement residence permit is not possible in your case. You should then seek residency regardless the fact your father is now a Spanish National.

Regards,