I don't know where to start! So much of what you have posted sounds familiar.

You haven't let him down at all. There is nothing wrong with waiting a bit to see if the traits he displays is something he grows out of. I did exactly that till I decided I had to know for sure and took M to be assessed. It is something you need to be ready for. It is a shock but then it can be a relief too. Remember that once it's over he is still the same gorgeous little soul.

I've been there with more than one Dr that knew he was Aspie as soon as we walked into the room.

Too social and vocal and familiar with people. To the point of being an awful pest to complete strangers.

One of my dear friends breathed a sigh of relief when I told her of M's diagnosis because she knew but didn't want to upset me so didn't say anything. She knew him from birth.