This post was very difficult to read.
I empathize with you, on so many levels.
First, I consider myself blessed to have known and currently know, unconditional love. I have it in my life with my wife and daughter and before they died, my maternal grandparents. Outside of family I have only received and given unconditional love to one friend, and he is of course, my best friend. I am blessed to have him in my life. I also have experienced it with 2 dogs. One living and one past. Every moment I am at home, whether awake or sleeping, my dog is close enough that she's touching me.
While reading your post I got angry. But not at you. My biggest mistake (regret) in my life, according to me, happened with my grandfather. I won't go into details, but suffice it to say, I have never loved anyone more. He died at 92. When he was in his late 80's, and after suffering a stroke, I managed to take him fishing, one last time. During the trip, he was handling a fishing knife and when I saw I went BALLISTIC. I yelled at him like I was an animal. I could see on his face that he was ver hurt. I still can't explain it nor have I really forgiven myself for it.
My only advice is to keep the happiest memories alive. The sooner you let go of the trauma, the better for your physical and mental health. You can't change the past, only how you remember it.