Antonia, you have very wisely written on many occasions, and often helped me. I share your sentiments, BUT have come to realise that if we are to survive we have to change our thinking, as you have also said. Yes, we have fallen short of our ideal. And that would have been the case also had your xh died. Nothing in this life is permanent and it is a dangerous fallacy to live with this belief, comforting though it is [i know, I have been there, and screamed against fate for what happened] But my parents endured the loss of my beautiful sister at age 25. healthy happy and recently married. So loss is a part of life, however unfair it is. Your h chose not to grow, and you are moving onwards.
In some ways it is a disguised blessing, hard to see, I admit(!), for if you had stayed together your xh would have held you back, and you might have been a lesser Antonia, perfect from one perspective, but limited in other important ways. The poet John Keats said in a series of letters to friends that life is about making your soul. This is the refiners fire.