He followed me up and told me this is all my fault, what do I expect after 12 years of no sex, I've created the atmosphere in the house, everyone is unhappy because of me etc etc. I was half expecting this response as he always looks to blame others for everything. But I didn't expect to feel as if maybe he's right and I've driven him to it. Yes, I do act cold towards him, but only because I plain don't like him or the way he's made me feel like a single mother for years, doing whatever he wants, going to gigs all the time, but he now says he does this as I make him feel unwanted.
The thing is, this is exactly how relationships break down.
One person does something, the other person responds by doing something else. At that stage, neither thing is probably all that bad. But it creates resentment. Slowly, over these years it continues to diverge and creates a situation where there is a huge disconnect but where neither person wants to be held responsible because they are no more (or less) responsible than the other.
Neither person has done any one thing that is particularly relationship ending and both people are kicking the can down the road in terms of dealing with it or addressing it. Both hope it will change, both put it to the back of their mind, both focus on other things, both avoid conversations, both think they are communicating disatiafaction in ways only they can hear (eg going to gigs, being cold, withdrawing sex, doing everything themselves) etc
In this situation, you have been waiting for him to do something so awful that you can stand back and say to the world, "See everyone! It was all him. I've done nothing wrong!" When the sitting back and waiting and building resentment was, in and of itself, wrong.
You half expected his response because he likes to blame other people for things? Isn't that exactly what you are also doing?
I haven't read your other thread so I have no idea what happened in the past but either you are both at fault because he was an absolutely useless dick and you didn't leave or you're both at fault because, like Mr and Mrs Twit, you've spent years creating an unpleasant atmosphere of building resentment together.
It's very convenient for all of us to find ourselves blameless and the other person at fault but it's very rarely that simple.
You could meet me for a few pints and I could tell you all about the things my exh did wrong in our relationship. You'd think he was a dick and wonder why I put up with him for so long. Or you could go out for a few pints with him and he could tell you everything I'd done wrong and you'd think I was a dick and wondered why he'd put up with me for so long!
The reality is that we were both at fault. Yes, he committed the 'ultimate sin' of looking elsewhere for sex. But when I think back over the relationship and how it broke down, it was exactly as I described above. Little things that chipped away at our sense of 'togetherness' that left us limping in a long dead 'relationship' where we rubbed along ok but neither of us could say we hadn't seen it coming and nether of us came out on top. All we could do at that stage, was make the best of it going forwards for the sake of the children. We did and they are both pleased that we finally did it.
You've both been playing your own long game, OP, and you're both just realising that there are no winners.