I like your list of goals for the week. When are you getting your puppy?
The list of thing to do when you feel anxious I actually got from a podcast, 2 therapists were both discussing how they each have lists of 10-15 things to do when they want to calm down. I'm considering doing my own version actually.
I really resonate with the being married to someone who evades self-reflection and change, I felt that my dh was like that and when he left my biggest fear was that this was another way of evasion. But from what I can see so far it hasn't been. I know you're in a different position because you asked your husband to leave. But then I think about how hard change is, and I think that actually I was fairly resistant to change too because I would complain and blame dh but not want to change myself. I feel like this separation has been painful enough that I will change permanently, and hopefully dh will too. I hope that your husband is having a similar revelation, it sounds like there are good signs so far.
Re the family therapy: could you talk to eldest about it? It sounds like you need to stay out of things maybe, because you getting in the middle and wanting to fix them both has been part of the problem by the sound of it. But thinking in advance of how to calm down if you get flooded would be good.