Hi Eunicorn, Welcome to the forum
I'm very sorry your family's being affected by the disorder at the moment. I was around twelve too when the disorder began to worsen...it's a very difficult age isn't it, made so much harder for your son with the autism along with all that's going on with this virus. I'm glad though that he's on the waiting list for CBT, but I think you're doing the right thing by being proactive with looking at ways to help him until that's available. The advice you've been given so far in terms of working towards cutting down on the compulsions is good...but to do that he really needs to understand how OCD operates.
That's something the treatment through camhs will cover, but I'd recommend getting hold of 'OCD Tools to Help You Fight Back - A Handbook for Young People,' by Cynthia Turner. And, maybe 'Parenting OCD' by Clare Sanders. They're both available from the charity's shop (and I think cheaper than through Amazon). If he understands how the disorder operates and why he feels the way he does, he might feel more confident about, and better able to start making some progress towards recovery. I would be tempted to hold back a little on ground rules though, at least for the time being - maybe instead of rules go with negotiation. Discuss with him if he'd be able to sit with the anxiety from not carrying out a compulsion for a few minutes, while helping him refocus by chatting to him about something he's interested in. From there it's really a case of repeating the exercise until he feels little to no anxiety. It's going to take time to come through this, but for children diagnosed with OCD the prognosis is very good. Yolanda's (a Management Committee member) son, was diagnosed a few years ago and with her help with the CBT is now doing well, and I think in complete recovery.
I think this is probably a daft question considering how much pressure you're under, but how are you?