@Healandlove I'm glad to hear that the little alteration in your behaviour (not moving to reconciliation first) did prompt him to take that step to be accountable. Breaking habits is already hard, but breaking relational habits, doubly so!
Have you heard of the concept of displacement? I'm wondering if maybe therapy is bringing up a lot of stuff that's been stuck within - for instance, if he was completely unable to express his emotions as a child, he may hold a lot of anger, hurt, and/or resentment that he never got to release. Our emotions gotta come out some time! And the thing about displacement is that we usually turn to a 'safe' person to express these emotions, i.e. if his anger would have gotten him punished as a kid, then the brain is wired as 'expressing anger = unsafe, potential for abandonment'. So when he finally finds someone who DOESN'T reject him for his emotional expressions, it means a whole bunch of them have come flying out at you. I remember asking my sister once why she always got so angry at me, back when she was really unwell. She told me 'It's cos I love you so much, and I know you love me too, so it means you will actually forgive me afterwards.'
I think @Ru-bee already nailed it with the ideas for burn out recovery!! Only thing I'd add is to reflect on/decide for yourself what your 'line' is - i.e. in terms of developing some boundaries around how much of his emotional volatility you're willing to tolerate. It might mean walking away from tense conversations sooner than you were before, calling a time out as soon as distress enters either of your voices whilst conversing, or asking for more time and space after a conflict for you to recover/come back to baseline.
And be sure to indulge your creativity and passions!! Dance! Sing! Paint! Skip down a hill! All things that can refill our cup 😊