LIO - sorry to hear about that rough conversation.
One phrase that has worked for me as a response (perhaps less wordy than what you have above about not doing work for him) is "I'm sure you'll be able to figure it out." You are right to let him puff around.
It helped me initially to think of STBX as having a MLC mental illness (even though it's not a formal diagnosis) because it was easier to forgive him that way. I used that analogy with some friends who were livid about his actions and it calmed them down, too. Once the forgiveness took hold I reframed it a little.
Since you've already offered to take S to him, I would not bring that up again. If he wants you to do it he can bring it up later himself. Remember that you've been fired, so you don't need to do anything to comfort him.
You've come a long way - stay strong. You can do it.
