Florence,
This is so terribly sad for your son. I'm sorry for him and for you that you have to go through this.
I too, found some hope and positivity in your post. I think you have shown your son that we can endure difficult times and life can always change for the better. I know these positive lessons can feel as delicate as a feather and these traumatic events hit like a wrecking ball. But I believe those positive lessons will endure and he will hang on to them.
He must be a wonderful kid. With such a complicated situation, step mom wants to stay in his life....I imagine she has a lot on her plate and is overwhelmed with everything. But to know, through all of this, that one of her priorities is to maintain a connection with him says a lot!
Sending you lots of hugs,
MamaKit