You are putting too much blame on yourself. It takes TWO to maintain a relationship or to repair one. No matter what you did, if your ex did not want to change, did not want to make things better to allow relationship to continue then nothing you could do would repair it. It would have taken both of you.
True that I am blaming myself. When you're married, things aren't always equal between the partners. Spiritually (not religious, but spirit) I'm stronger than him. This isn't a perjorative assessment, it's why it's my fault. He is always focused on, and doom-scrolling on how awful everything is. He says it's logical but it's not, it's sick to be negative all the time.
Like you said he is stuck like that. From what I've seen, being an older Aussie guy he doesn't or can't admit he is frightened of and needs help with what is happening to him. I shouldn't have let him get away with the nastyness, the put-downs, and other abusive acts. I did react very strongly, I mean who wouldn't. My reaction was to abandon him, to break promise I made when we were married. But yeah, he may have my possessions and some nice paintings, just he doesn't have me anymore.