What safeguards should I have aside from a safe word for scenes that could possibly reactivate my trauma?

When I was a kid. I had a highly traumatic incident where four or five other kids held me down on a concrete ramp leading into the building until a teacher noticed and came over to pull them off of me. This incident could have been particularly fatal due to my autism. Ever since then, I have had an overwhelming trauma response to being restrained in any way. I'm worried that this could impact my ability to indulge in my more submissive side, which I'm hoping to explore in the community. I've been thinking about playing around with that side of myself already as a kind of exposure therapy to help me get over that incident. What would you recommend to make sure that I don't push myself too far? I often have a fawning or freezing response to stressful situations, so I'm mainly worried about having a freeze response and forgetting the safe word or something similar. What would you recommend in terms of aftercare?