People who are trauma bonded develop a psychological and, yes, physical addiction to their captor. Captives often put aside their own needs and do everything they can think of to hold onto the relationship, mistakenly believing that if they can find the key to the captor’s mean behavior, they can change them. You can’t. As you said, your ex is narcissistic and violent. Your ex being a meth addict only makes detaching from him all the more difficult for you. Addicts are adept liars and con artists. There is nothing you can do to make him change.
You’ve already taken steps to help yourself. You have ended the relationship. You recognize that the relationship is not healthy. You recognize that there is something wrong with your ex that makes changing him unlikely to impossible. You are not allowing contact (I hope). That took courage and determination.
Your feelings of love or maybe need are at war with your good sense. Do acknowledge your feelings but then try to figure out how this guy got such a strong emotional response from you. Chances are, he figured out that you have some unmet and painful need and he honed in on that.
You are in your 50s. Maybe not having a partner at this stage in life is lonely. Maybe when you met you were more vulnerable than usual because of some other loss. Recognizing how your abuser got to you is an important step in learning how to protect yourself now and in the future.
Then allow yourself to take this one day at a time. As with any other addiction, breaking your addiction to him will take time. Don’t allow yourself to believe that you will always feel as you do now. Make good, healthy choices for today and stick to them. If that is too difficult, take it hour by hour. This will help you develop a habit of health.
Not so finally, give yourself permission to get help. Talk to a therapist. Join one of the online forums here at Psych Central, and/or talk to people who love you to get the support and guidance you need.
I wish you well.