The vector of you explain -> he changes is unlikely to work to your satisfaction. Talking about it calmly after the fact, how does he explain why he cuts you off so frequently and thoroughly? Could the two of you agree on a neutral safeword for when he falls into that mode, so you can both pause and breathe a moment? That allows you to stand up for yourself without having to turn up the volume, and allows him to see his disruptive behaviour for a moment without feeling like it's an attack. It's an assist on the brakes he doesn't have, and a minimally-disruptive, planned intervention together to manage something that's traditionally led to hurt feelings.