Haunted I was hoping someone else would reply because I worry that I may not say the right things.... but here's my thoughts. Maybe this will bump your thread for the support you need.
I remember seeing your update 13 May and feeling like I got exactly what you said and feeling concerned. I feel it was the same position I had found myself in. My take on it is that when you tried to end it you were doing the right thing. I tried too at the beginning of this year and ended up trying to fix things, it's my depression etc.
My thoughts about your situation.....you need to leave, him changing is not good enough, he has behaved as he did because of a huge problem with how he sees you, has he really changed that? Does he get that? Or will it be shit again, and you will have lost a bit more of your sanity, a bit more of yourself.
The "trying" period where he behaves differently has probably been a headfuck for you because it undermined the clarity you had found. The clarity which is both terrifying when you see what your relationship is, but at the same time brings relief because it makes sense of the depression and anxiety you feel.
Even if he has changed, is it enough that he does it to keep you? Is that love? I don't know.
So hang on to what you know. And ignore the niggles.
I want to say good things about leaving, about it being ok, about you can do it.... but I haven't actually done it yet. But I am trying to believe those things.
I may have totally projected my own feelings here. But some of the things you say feel so similar to things I could have said.
I hope there will be others along to share their wisdom and give you the encouragement you need to work out and do what is right for you.