@User048261940582, my heart goes out to you. Your H’s betrayal is truly reprehensible.
While you’ve been giving your all to your marriage, family, home and work, he has been pursuing a teenager in a fantasy scenario where ‘they’ve been there for each other’. In truth, he’s been exploiting this power imbalance and getting off on this girl’s flattery, attention, and young body. He is a morally bankrupt, pervy creep of the highest order.
His mockery and mistreatment of you and the children are beyond the pale. He is ‘that guy’ who makes a choice to be hateful to his Wife at home while he is publicly humiliating her. Summon your anger and fierceness and channel them into a laser focus during your interview.
As for his ludicrous message asking if you want to fight for the marriage after he has destroyed it via his unethical, adulterous actions, there are no words. Please ignore this and all of his manipulations, and only engage with him using gray rock and email to make contact arrangements.
@User048261940582, try to practice
self-care while embracing your children and work. Lean on trusted loved ones, and consider accessing IC to help you move through the grieving process.
I strongly advise you to consult with a solicitor to learn your options and make preparations to file for divorce. If my H had shat all over me and my child like this, I know that I would never be able to regain any trust, respect, or peace of mind, so it would be over.