I don't have any specific advice, just wanted to share I had a very mixed reaction to this.
First, your H shared some deep feelings with you, and you validated and showed him a 180 on prior behavior. Fantastic!
Second, having gone through similar experiences myself (both in your shoes and your H's shoes), it is part of the process. It is heart-wrenching. It's awful. As best as you can, do not connect any of this to hopes of R.
And finally, I was upset on your behalf, although I'm not sure it's really fair to be. I feel guilty if I feel I am using my kids as an emotional crutch, and I felt a tinge of that in your H's interaction with D4. Perhaps I am not being fair.
Overall though, whatever happens in your relationship, establishing a more positive connection with your H will enable you to be better co-parents which is a huge plus.
