Thanks, Labug.
It's interesting that you bring that up - it reminded me that just before bomb drop, my H and I had been on a cruise with my parents and my dad got very sick - nearly died in fact.
H was the one who took over and cared for him in a very intimate way (toileting/showering, etc) as my dad wouldn't let me do it, and my mum was too frail.

The day after we got back, H announced he 'couldn't do it anymore'. I think the pressure he felt seeing my dad nearly die and having to be the one who cared for him was the straw that broke the camel's back. He'd already pretty much detached in his mind, but the need to be the responsible, caring SIL, H, Father just produced too much incongruence for him. The A with OW had started back up and this is when H started to refer to himself as a 'scumbag' and 'dirtbag'.

So, thinking about what you said, I need to realise that H cut those ties 7 months ago, and I've been clinging on under the belief that he'd have to come to his senses at any moment and see what he's missing in leaving us.

But once you cut those ties, it must be almost impossible to go back. And in a sense, there is no 'going back'. It can't be done.

Which is why the emphasis has to be on going forward; on things, and people, being different.