This is a wonderful post that seems to be a very clear emotional self-portrait, and thank you for writing it.
Might I suggest, however, that there could be an error in you emotional algebra here. 1) The terror you feel is your inner-child's existential crisis (many of us, including me, know this feeling all too well); 2) it is hard for you to hate your attacker because he was just a belly and an erection during the attack; 3) Although you don't blame your young self for the attack, you now hate him for making you feel these new overwhelming feelings. Do I have this right?
First, I'm sorry you're now in touch with existential terror; it's a close companion of mine as well. But it's not fair to your young self to blame him for breaking the seal on this dormant pain. He needs you to feel what he feels so that you can protect him from it.
If you're blaming and hating him for it, then you and he aren't going to get along very well. I find myself using the term "psychic alchemy" when thinking about this issue, both for me and for others. It's a process by which we learn to take negative emotion A and turn it into constructive emotion B; I am not good at it, but that's the idea.
I feel like, with me (and perhaps others), the abuse caused this certain kind of energy to be unleashed inside of me, like nuclear energy, which if I kept it bottled up would rot me from the inside out... but if I can find a way to channel it outward, it becomes this laser beam that helps me accomplish the seemingly impossible. (a nuclear powered laser beam, apparently. Sorry for the mixed metaphor.)
This appears to be similar to what you're experiencing, too, which is why I bring it up. I'm not sure how to suggest you move from where you are now (hating your young self for making you experience his terror) to directing that anger outward in a constructive manner, but that's the goal.
Imagine your present-day self in that toilet stall, watching it happen. Who are you angry at now?
But he grew old, this knight so bold / And upon his heart a shadow / Fell as he found no spot on the ground / That looked like El Dorado.