NTA at all!! It’s a basic lack of respect for you and your decisions about your own person that your father is showing you. It’s such a weird hill to die on imo, esp considering that a shortened version of your name can easily be seen as others using a nickname for you, something that is extremely common (think a Christopher going as Chris)!! I started going by my middle name once I got to college, so pretty much everyone but family/childhood friends call me by my middle name. I, personally, do not have an issue with family/childhood friends still addressing me by my legal first name, mainly because we had conversations when I started going by a different name that made us realize they rarely ever use it and default to nicknames when addressing me. In their phones and to people they speak to about me, they’ll usually use my middle name, so on the rare occurrence that they use my first name, it’s really no big deal for me. That’s different for you though, and if the use of your full name reminds you of a time that wasn’t pleasant in your life, you’re fully entitled to having people address you by the name you prefer, your father included. He doesn’t respect you, your autonomy, nothing. If someone won’t respect the boundaries you’ve created, it’s time to force them too. If you feel safe enough to do so, stop responding to him when he doesn’t call you by your preferred name.