Ambi - my dear, you just got the MLC script. I am so sorry, but as Job said, your h has a long way to go.
I agree, do not reply in a hurry. Do not attempt to try and reason with him, engage in discussion or any of that. Believe me, it does no good. If you do make a good and fair point he will simply change the ground of the discussion.
You will get better advice than mine, but here is my 2c.
Thank him for letting you know, say you are very sorry that he has come to this decision, but acknowledge that it is his choice.
Then go dark, really really dark. he wants out, and he gets it. That is the deal. It will be easier on you, having no contact. Trust me on that. Seeing them in full blown MLC is a world of hurt and pain.
See a lawyer, check the financial position, and protect yourself NOW. The one thing I wish I had done sooner. i kept thinking he would not screw me over.
Allow yourself to feel bad. It isn't about you, it is his problem. Right now you feel shocked, hurt and probably a bit numb.
You have your girls, and your friends. Please be very gentle and nice to yourself. Then dry your eyes, pull up the big girl panties, and make the most of the rest of your life.
Your husband might come out of it, and he might not. You can go on loving him, but he is not to be relied on for anything right now.