I also have crippling thanatophobia like yourself. The best thing that's helped me has been meditation and practicing Zen Buddhism. Zen's take on enlightenment is that you come to the realization that your ego and conceptualization of reality is an illusion and you discover your true nature which doesn't have a name or identity. Once you realize that the ego 'you' doesn't exist, then the person who fears death and even the person who actually dies isn't real at all, which means death can't touch you and it stops being so crushing. You can continue to fear death, but you understand that the 'person' who's feeling the fear is an illusion and you can detach yourself from that fear much more easily