Gwen, I'm glad to read that the new job is going well and the girls are doing good too.
As for the final separation agreement, you h probably already considered himself divorced when the switch was flipped. What you have been feeling, i.e., like a failure, is very normal after having the bomb dropped. Your h had choices and he chose the wrong ones and one day, he'll probably think about those choices and wonder why he made them. By then, you will have moved on.
I think you've been handling things quite well and the advice/support you have been providing to others as been excellent.
Hang in there! Things will get better.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.