First things first.. congratulations on the positive news on the negative results. You're in my heart and prayers.
Second thing.. Your email expresses how you feel, but you're apologizing to him. As far as I can tell, men numb out if it's not simple declarative sentences.
I still will try and reassure him and I wonder why afterwards? His agenda is all about his new life and companion, it has NOTHING to do with me aside from making sure he has minimal financial stress. My reassurances or apologies keep me susceptible to working like a team in our former union (which he isn't doing) and subservient in a way.
You've got testicles too! Just spell it out simply.
"Don't leave our son alone in the house. It's not safe for him and against state law."
Write to him like Ready says... With no expectations or intention. There's no need to apologize for anger or judgment on your part. There's almost no need to tell him you're moving on. What is the message? You need your own space as you make a life for yourself. What if it upsets him? It's his issue, not yours.
As long as you or I continue to live our lives through our spouses perspective, we're stuck. It's not about them, it's about us. I work on not letting my mind wander to if he's getting remarried right after the divorce, how I'll manage without the security of a relationship.
But guess what?
The more you try, the more you create your own life. You'll find yourself doing things you never would have tried, like me and choir and finding that I have a wonderful singing voice.
Co-dependency builds an isolated world, something I've done. But those baby steps out help so much.
You go, Ms. Heart... you've got the strength, beauty and heart to make it all possible!