Getting out

I realize no one here knows a definite answer, but I'll ask anyways - what is to be expected after permanently cutting all contact with a disordered person (narcissistic/sociopathic/sadistic traits) I once was in a relationship? I am not splitting this person black, I did and do love them still probably, but I'm no longer able to deal with their attempts to control me/aggression/sadism. It has gotten to a point where I feel forced into "trying it just one more time" by getting all the people around me involved in pushing me to answer his messages. I do feel very split myself as I've known this person for a long time and did promise to always be there in some form (most people/family in his life have failed him, and this was much more than an empty line to me, as lame as it sounds), but the person he once was and the one he's becoming these days have nothing more in common. I have extremely hard time accepting that, once I cut him off, he'll consider me traitor/enemy for the rest of his life.

I know what he's capable of when he hates. There will be no compassion nor consideration for everything we've been through. His retribution will be covert and least expected. We share a social circle/profession/friends/mentors, etc, etc. I will frequently run into him in parties/birthdays/events and all the places I usually go out to. Neither of us is planning to move any time soon. He knows me very well, all my weaknesses, all my strengths.

Getting out (for good, this time) is not questionable, I'm going through with it. But I do admit fearing everything that will happen afterwards. I'm unable to predict anything as the break-ups in the past have never had this time it's for good and I reject all contact undertone, all my little "escapes" had an expiration date. He was also never this aggressive in the past, he was mostly proud which seems to completely lack now in his behaviour. He threatened to ruin my life in the past when things were not going his way but never went through with anything (as far as I know). I would never do anything to cause him harm, no matter its necessity, so my question mostly revolves around:

How do I get out of this with as little consequences as possible?
Is my fear based on real or perceived threats? He hasn't done anything other than forced me to answer and "give him an hour to tell me his detailed plan of fixing everything that was broken", + not wanting to take no for an answer. A part of me knows that his behaviour when we were last in contact could be described by some as psychological abuse (one I've willingly stayed for, yes, but it did push me soon enough to one of my "escapes"), the other part thinks I was being too sensitive. I'm unclear about it.

I've caught myself not giving him a definite answer out of fear of retribution and even figuring out alternative ways of agreeing, then getting him to lose interest. Pure existance of this fearful feeling made me realize (cognitively, at least) there can't possibly be any love here, only pathology. I've never felt fear before in regards to his actions or personality, I always thought I could handle whatever he sends my way (am I equally disordered?). Whether it's my anxiety acting out this time, intuition or something third, I'm honestly not sure, but I can't get rid of this feeling that he already realized I'm not coming back this time and will use/is using everything at his disposal to prevent me from it. These promises of new ideal relationship where we'll work on all our issues (everything I wanted to hear a year ago) might as well be a trap to punish me for the previous little "escape", rather than "having enough time to think things through and realize he can't allow himself to lose me".

How do I deal with this? What do I expect when I go through with it? What are the odds of him simply moving on? What are the odds of my hypervigilance/anxiety acting out and blowing everything out of proportions? (What are the odds of any of you really knowing the answer to any of these questions? - yes, this is partially venting)
I'm unable to get my attitudes/feelings in order as I seem to be expecting some sort of attack from a person I don't at all perceive as enemy. I also seem to have lived in an illusion of moving on with my life for the past 6 months.

I guess I'm hoping to hear personal experiences if there are any, or an advice on how to successfully pull out of toxic relationships for good. (I'm also not looking forward to anyone splitting this person, but rather approaching it as a mathematical problem with possible outcomes and/or a solution if i'm lucky enough. )
I'd rather not write anything further here, but do have the need to press "submit" button for the above. I want it to stay as a reminder, if nothing else, I do seem to forget faster than a goldfish.
ps. for the record, I was not planning on writing this much text