I agree with your assessment Orm and I think your husband has been 'played' to a great extent. I think this woman has grossly exaggerated tales about her husband's 'abuse' to the extent that it's in fact non-existent, whereas her own affair is of course emotional abuse in itself, isn't it?
I think she is the architect of all the rumours, wanted your husband to leave and make a grand sacrifice - at which point she would have withdrawn, having 'won'.
I agree it's very important that he makes these realisations, but the most important one is that she did not love him. Nothing she has done conveys love.
Once that realisation hits home, the usual progression of these things is that he will hate her, at which point you'll start to hear a few more stories from the affair, but told through his by-now different lens.
Now for a while, that hatred will get in the way of him taking full responsibility for the affair and he will start to blame her for more things and you might even find yourself doing the same.
But it's a process, this business of recovery - and that phase will soon pass. The next phase will be some acknowledgement that although she played him like a fiddle, there were things he did too that were dishonest towards her normally in relation to the impression he was giving of your marriage and his happiness in it.
Orm I think your husband needs to read about how much 'mirroring' goes on in affairs, which is a fancy name for lying to eachother. He also needs to see that these rumours could have come from no-one but the OW and to question why a woman who was allegedly in an abusive marriage would take such risks with her own safety and the emotional wellbeing of her children. You're dead right, the scales need to fall from his eyes and he needs to see through the lies and the motives.
On a human level, he will feel a bit crushed that he wasn't adored after all and then he will feel utterly stupid that he was so naive not to realise this at the time. There will be some maudlin self-pity about being an old fool, but he must not wallow in that.
One of the things he will realise is that he needs to work on his assessment and judgement of people's character. I have a feeling that he's always relied on you for that and trusted your judgement more than his own. Because once again I think this affair was all about the feelings it gave him about himself and all it took was a belief that he was worshipped, to make him vulnerable. What was missing of course was an assessment of the motives of the 'worshipper' and then later, the value he placed on the person who really loved and respected him - you.