Oh Connie, you poor sweetheart - really I feel for you.
Let's break some of this down a bit more. I think it helps.
Saying I cant explain is something I would never think of saying. I've always HAD to explain
You've not only had to explain. Just telling the truth, without fear, would be easy. But you've had to explain when someone has been already convinced that your explanation isn't true. So it's always an uphill struggle. It's a minefield. You quickly weigh it up - if you tell the truth (you were going to the supermarket to buy food for his supper, but you bumped into your friend and were longer as you had a coffee) - will it be OK? Will he be angry because you spent time with the friend? Will he hate it because he worries the friend will tell you how bad he is? Will he be jealous, and also angry because he didn't hear exactly what you said when you were spilling your thoughts and feelings? Were you poisoning the friend (and possibly wider group) against him, when he wasn't there to tell them how it's all your fault??
You had to explain, but were worried about explaining. Wow. Just think. Now you don't have to explain : D That's great! You don't have to! Nobody is going to hold you to account! Nobody is going to take it wrong and get angry for something perfectly innocent. Nobody is going to make you feel bad, and also sad inside at your situation and how it could and should be so different.
This second guy - if you don't give him an explanation, it doesn't matter You aren't obliged to. You've been fair and nice enough already. Clear conscience. And he isn't close enough to hurt you. So just send the text.
As for writing please don't contact me any more - I agree it's the moment of cutting contact, but I expect he will try to talk you round, whatever you say. So I think maybe what you need to make clear is that this is the end of you contacting him This is it. Last message.
Perhaps you could add:
I'm not going to be in contact any more.
Then whatever he says or does, you've made it clear.
And, you're so welcome to whatever insight I can give you. I do think that lots of people have been through very similar situations, and it really does help to know that there's a crazy pattern here. It's all in fact very mundane. Nothing special. Just standard madness. I'm sorry that you've been subjected to it. But it really is something that you can move away from. The second guy is a good lesson for you, going forward.
I'm not intelligent enough to break things down This made me so sad for you. It's not about intelligence. You've been so overwhelmed by it all, and so in it, for so long, that it was hard to see what was going on. Confusion tactics are part of the pattern. You can't think. You don't know if you're coming or going. You're just in a state of survival. Time doesn't exist. It's hard to reflect and get perspective.
So don't ever, ever be cross with yourself. There's no defence against straight abuse. So you just have to get out. And you have xxxx