I can imagine that there are no words to put how you are feeling. What a huge hurt and loss. I am so sorry! I am praying for you and I know that the Lord is close to the broken hearted. I pray that you will feel his peace and presence. I am so glad that you have your children to support you through this, as they too are working through their own feelings.
The panic attacks can be a normal part of the grieving process as it is all very new and you are trying to adjust and work through emotions. Loss/grief can come out in all kinds of ways. It sounds like you have a support system, but I know that there is a nation wide (assuming you are in the USA) Divorce Care (https://www.divorcecare.org/findagroup) that I know has been helpful to many people walking through divorce situations.
My best advice, though, is to take it one day at a time. These kind of situations can be really overwhelming in the moment as it is new and a lot to take in.

Practical advice: get a lawyer and protect yourself financially. Do NOT think he will be fair and honest, that he would never take your money. He now is listening to her and she is saying how he needs to take care of himself. Rough to hear but true. Find a therapist- you need to talk with a third party and vent and talk through options. It is a tremendous help. They see things with a different eye and can help you know you are the important one now. Also, think about anti-depressants or anti- anxiety medication. It will really help you over the rough spots right now and help control making impulsive decisions. I suffered for months before I accepted I couldn't just tough it out. Emotional advise: telling you what my therapist told me - you are important now. Pamper yourself. Get manicures and pedicures. Do indulgences that you used to think you didn't need. Rent a movie that makes you feel good. Arrange a girls night. Tell yourself you did not deserve this and you owe him nothing. He made a conscious decision to do this. He wants the best of both worlds it sounds and for you to feel sorry for him because the kids won't talk to him. My ex did the same thing and blamed me because his family sided with me. He kept asking them that didn't they want him to be happy? He couldn't understand that everyone felt his cheating was wrong even if it did make him happy. Think about only yourself now. You don't need to be polite or available or considerate to him. You are going to hear the same theme from others who have been through this. In the beginning I thought if I was nice and just pretended that he was away for awhile and I was ok with it, he would come back like nothing happened. And I was miserable and eating myself up inside. Take care of yourself !

I'm so sorry you are suffering through this.
I know, just how incredibly painful it must be.
My husband left me, without a word, 3 years ago. He's never been in touch with any of us, me, our children, his family.
But I divorced him, we were married for 33 years, together for 39.
Worst pain I've ever felt.
But I'm still here, and if I can do it, anyone can!

Reading this thread literally made me nauseous. You soon to be ex is trying to have it all his own way at your expense. I hope you move from denial and confusion to anger pretty damn soon, cause he is really taking advantage. Keep giving him enough of your time and attention and he'll have it all switched around so he's somehow the victim.

First he should not be spending family assets on gifts for his new girlfriend or what can only be described as dates (taking her out to lunch). Then to have the nerve to prioritize dating his new girlfriend while he's still married to you and telling you that he NEEDS you in his life? Well, that kind of selfish behavior proves what kind of person he really is. Of course he is telling you all how sorry he is. He's tearing everyone's life apart for his own selfish reasons and honestly believes he deserves absolution in the process.

I've got an idea. Why don't you concentrate on protecting yourself and your children until the divorce is final, then waste your time worrying about whether or not to forgive him. To talk about forgiving the person trying to drown you while you're still in the river is a bit foolish. There is a time and place for everything, now is certainly not the time to be thinking about forgiving him. He's wronged you, continues to rub salt into the wounds by not even having the decency to leave off dating his girlfriend until the two of you can separate fully, much less get a divorce. He needs to earn forgiveness with more than just lip service.