I can appreciate the part of you that wants to know what happened, but I guess there isn't really a way of finding out for sure, and as you've said, there's also the risk of more information causing further distress.
Sorry to hear that you've relapsed with self harm. Have you ever had counselling specifically related to abuse/trauma? Perhaps that would be something worth exploring.
I'm glad you're able to keep yourself safe from this person and are avoiding him as much as possible. Has he ever acknowledged anything that happened?