I don't know your full story, but I do know about N's and cutting supply. (Unfortunately

). As others have said, you need to stay strong, in any way you can, and maintain the
no contact. It is hard, and I can almost promise you that his demands will escalate. This is the hardest part. MAke sure you are safe above all else, don't listen to anything he says. I found it very helpful to have one sentence that I used if contact was unavoidable " No comment" or something similar that doesn't give much opening for a reply.
It will get worse before it gets better as he does everything he can to get you back (I had late night phone calls of vitriolic abuse, followed by flowers and chocolates outside my door every time I opened it). The
only thing that works in this situation at all is to be consistent. No matter how hard it is, no matter how much he begs or rages, just keep consistent. A very effective tool is to show no emotion. This is the hardest piece of acting you will have to do, but it is really good at helping to cut ties. I think it is because they feed off your emotions, that is what makes them tick - your emotional state. Just pretend as hard as you can.
I learnt this the hard way. I tried so hard to cut contact (although, I was pregnant with his child which did complicate things. Again, I don't know your story, so forgive me if I am being assumptive

) but would fail. Looking back, the times I tended to fail were times where he played on my emotions. "Think of the baby, we need to be friends. I won't ask any more than that. Just friends" or something similar. There will be a weak point for you too, try and identify it before the N does and be prepared for it. Either that or the rages would get to me and I would cave in for a quiet life. As soon as I did, the boundaries would be pushed and broken and the whole cycle would start again. Contact
always makes it all worse. The N cannot accept that you don't want him, he cannot accept you are seperate from him, and he cannot accept that you know what you are doing. These are all challenges to him.
Be as strong as you can. Find ways to avoid answering emails. This is all
so much harder than it sounds, I know this - I am not going to judge you for anything you do, I am just trying to offer advice from this side of ending a relationship (3 long, long, long years ago). Remember that to an N a brief email is anything but. Anything from you at all is supply and he will work on it. There is nothing to fear from not answering, as long as you are safe.
I feel so much for what you have to go through. It was (and still is ) the hardest thing I have had to go through so don't berate yourself for any mistakes you think you've made. I think as N victims we have got very used to the mentality that it "must be our fault" that it is hard to shake that. You are a person in your own right, you can make decisions and you can make the
best decisions for yourself.
I hope this helps. One day this will be less than it is now, just keep safe and be strong. I will be thinking of you.

Cadbury