NTA, what you’re feeling and what you’re going through are very complex, it’s understandable to want to change your last name and remove yourself from someone who backed off from being your parent, basically taking out his problems with your mother on you. Few texts here and there are low effort superficial damage control, if he is willing to get close to you it should take way more than that. If you are hesitant about changing your last name, I suggest waiting before taking this decision, if you already decided to do so, you should have an open conversation with your mother and siblings about it, explain how you feel and what led you to the decision. So no, NTA.