I find CotswoldGrannies post deeply, deeply disturbing, it is in itself a classic example of victim blaming.
Yes, we do have threads and stories on here where it is clear thatthe OP is probably the author oftheir own misfortune. But absolutely not in this case. Nothing, but nothing makes a WhatsApp group led by a husband with the children, whose sole purpose is to blame one person for everything that has gone on in the family and to denigrate and demean them, acceptable.
I am shocked and appalled that anyone could be so crass as to suggest this. In fact CotswoldGrannies post is so insensitive , I find it difficult to think that it was written with a straight face.
Most people who read other family members phone messages, do not set out to do it, but pick up the phone and see something that makes them go further. All this angst that you read his ohone messages, forget it. Once you has seen the first you had a right to go on.
To discover that someone who you loved and trusted, could let you down like this must be so devastating. How long has this been going on? Is he the reason your relationship with your daughters is so bad, because he has been constantly criticising you to them and feeding them negative attitudes to them.
I do not think I could even stay in the house with someone who can behave like that. It would make me feel that my whole marriage was based on a lie. If your job is sufficient to make it possible, I would just rent some accommodation and move out. It will give you a breather and a chance to seek counselling. There are courses and one-to-one counselling available online.
What your husband has been doing to you, even if you have only just discovered it, is emotional abuse. It is a crime and a cause for divorce. It might be worth your while to speak to your local Women's Refuge. Eeven if you do not need the protection they can offer, they will be able to give you the practical and emotional support you so need at this time.