More traumatic at the time doesn't neccesarily equal "worse."
And no, he isn't responsible for it at all. Was it a bad choice? I would say so. Should he have stopped him? I believe that he should've. And everybody has a choice, in everything that they do. It is ALL about choice and the perception of that choice. I mean, you think Peter is responsible for Ben's death, right? Well, what about Ben, what about the choice he made to put his life in danger knowing that he had a wife and a family that counted on him? Should we blame Ben for all of May's and Peter's pain? For acting without thinking of the consequence of this on them? What about his "responsiblity" to his family? Should we blame Captain Stacy for putting his life in danger every day, knowing that he has a family that loves and depends on him? Or even Gwen, staying and trying to save all those people, when she knew she had brothers and a mother and a father who all loved her and needed her. Should we place blame on all of them? They all had a responsibility to the people who they love and who love them back, and yet they ignored it. Should they be held responisible for all of their family's pain? No. And neither should Peter. He made a bad call, and he should feel guilty for it, it's only human TO feel guilty, but that is not what Peter should and needs to take away from the situation AT ALL. He shouldn't be driven by guilt, he should be inspired by goodness, by his Uncle Ben's ability to do what's right. With great power comes great responsibility, right? WRONG. The responsibility is always there, and Uncle Ben showed that. He didn't have the ability to do what's right, he had the opportunity to do it, and he took it. That's what matters, that's what's important. Not guilt, not pain, NOT revenge, but what's right. His mistakes do not define him.
And I'm confused, Peter isn't exactly flaunting his identity around.