You have every right to be enraged at her as well as him.
Some on MN say the only person you should be angry at is your ex for betraying you.
So many men think they can just snip through the bonds of marriage, family and fidelity and head off elsewhere without a care, start again, and expect the ex to be cool with it, accommodating every whim. I honestly think a lot of them have a bit missing.
But in my view women who deliberately throw a grenade into another woman's marriage, destroying her happiness, depriving her of so much? When they could say 'no - you're married'? They deserve that rage, too.
You're struggling right now. Still in shock and despair at what the pair of them have done to you. If you can, some therapy might help you deal with the rage, grief and despair. Letting it out is probably healthier than trying to suppress it. Help yourself accept, heal and move on.
On a separate note, you are now separate individuals. It's quite likely that you both might find love and happiness elsewhere. Maybe she's his forever person, maybe once she realises she's got a lying cheating bastard in her life, things may change.
But he is always going to be their father and a relationship with him is not necessarily a bad thing for them. And if he does have a change of personality and become a good partner, then she will be part of that.
A hard road for you - try some therapy to help you heal.