OP didn't blame the student for the crackup, and instead looked for things he could have done better. In addition, he's understandably concerned about his career. That shows self-reflection and honesty to me. Way too many other threads on here, and other forums, start out as "I didn't do anything wrong, everyone's conspiring against me, and...".
I've read a lot of accident reports, and I'm a bit familiar with risk in other fields. People generally don't kill people because of lack of skill, but rather lack of judgement. If you include pilots and doctors that haven't had the sense to quit flying/operating when they loose their skills in the judgement category, it's more.
To hindsight2020's point, I believe, a lot of people don't care, or think they're so good at their particular field that in their head they're special and the rules don't apply to them. Those are the ones that I try to avoid during the interview stage, and if possible get rid of after hired...but it doesn't always work, and not everyone can do that. My take, though, is OP isn't either of those.
My guess, though, is that OP's real mistake could have been instructing before he was ready, or before he was familiar in that particular aircraft. He mentioned the electric flaps on the 172. So most of his time is in PA-28's or Diamonds, and he doesn't have a lot of hours PIC 172, then that could have been a thing. I'm NOT a cfi, but would think a pilot would want to know handling of the instructing aircraft backwards and forwards before doing primary training in it. Just a guess, though.