Sounds like a lot of insecurity on his part -- not unexpected. And I find that a lot with my H. A lot of his dysregulations at me are, at their root, about a fear of losing me.
It matters what you agree to. Yes, he will probably get triggered and fall back into patterns. Progress is not linear. But it can get better, especially if you both work on your communication skills.
When my H had his breakthrough, we talked about things and came up with some rules for communication: no serious discussions via text or email, no serious conversations when alcohol was involved, no serious discussions after 10 p.m. And we came up with a safe word either one of us could use if triggered. Once it's said, we go to separate rooms for 30 minutes. If one of us is still upset, that's another 30. That's what works for us. Your needs/wants may be different.
What are some rules you think might help your situation? Feel free to share what you're thinking of saying and we'll be happy to give pointers and feedback.
When going into the conversation, be sure to use "I" statements, not "you" statements, which come across as criticism and may trigger defensiveness. Mutt gave a good suggestion with SET. You might also consider reading up on
DEARMAN.