Have you been to any parenting courses around ASD? I ask for two reasons, the first is that you say that he ‘is’ ASD rather than ‘has’ or ‘is on the autism spectrum and the second is because in ours it was hammered home that you have to be very clear with communication, not too wordy and say what you want.
It sounds like a different choice of word would have been more effective but I totally get that parenting a child who is on the spectrum is challenging and a massive case of trial and error.