22(M) with a narcissistic mother How do I go NC ?

Hey guys, I am a student still living at home, with my two parents and my two siblings. I haven't felt safe here for a long time, but have been trying to just get by and make it to the end of my degree as soon as I can. I finish in four months and I am hoping to find any job I can somewhere near where my long distance boyfriend lives as soon as I finish, so that I can have time and space to figure out what I want in my life. My mother is frighteningly homophobic, and I am further scared of judgement as my boyfriend is 32, and while I know that my relationship with him is healthy, equal and genuine (despite the age difference) , I am afraid of the way it may be perceived by family members. As such, for the time being my relationship with him is a secret from my parents and siblings, but my friends all know him and like him. When I graduate, I want to just leave my house and live with him for the summer, but i don't know how to do that whilst hiding who i am living with from my parents. I feel ready to tell my dad the truth, but i am unable to tell my mother. I don't want to cause distress for my younger sister, but thankfully she understands that our mother is the one at fault, not us. I guess I am looking for advice, i think the best thing to do is to find a job and a place to live near where my boyfriend lives, but perhaps not live entirely with him as that could get complicated if my family visits. I want to go NC or at least close to it, but while i still live at home it feels hard to understand how to do that, especially as I am not sure that decision would be supported by my siblings and others. What do you guys think I should do? I can't imagine being able to go non contact with my mother, especially while my younger sister will be still living at home for the next 7/8/9 years at the very least.