Hi Scout, Sounds to me like you handled that situation well, not badly at all. You listened, you validated as needed, and he actually calmed down and opened up. The fact that he was thoughtful and acknowledged that he's acting in his own self-interest, not S1.5's, seems like a pretty big step on his part and a huge shift from the beginning of the conversation where he was just trying to justify his own sh**tty behavior because you were "being a bitch". (So cliche, by the way. Cue eyeball roll.) I know it has been hard for you to be calm in those situations and it sounds like you really did well, maybe you said something at the end that came from emotion but whatever. You learned something in the process (he acknowledged his selfishness) and use that to help you continue to detach. You're amazing. Keep it up.
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing