Jesus H Christ some people are insensitive.
Ignoring that part of the thread, something you said earlier about not knowing what else to say to H's colleague's email, as you wanted to remain dignified, struck me.
I totally agree that maintaining dignity is vital (though not always possible!) but I wonder if you are mixing this up with something else, taking it to mean not giving any details?
IMHO it would be very helpful to you not to keep his dirty dealings a secret.
Saying to the colleague, something like this...
"Thank you for getting in touch, it is much appreciated.
"As you can imagine, discovering my husband was having an affair and engaging in sexual relations while at work, has been devastating and his subsequent treatment of me and the twins has been shocking.
"However, we are coping and are getting through the days - as painful as they are - and hoping to slowly heal and move on in time.
"Your email has meant a lot to me, it is good to know where there is support as the twins and I put our lives back together.
All the best,
Phee"
...gets the message over while remaining dignified.
He might get away with this but he's should NOT be allowed to re-write history nor minimise the damage he has caused.
Dignified = good, keeping the facts quiet = not so great for you.
They are not mutually exclusive.
Well done so far, lovely, you've been a star.