I'd agree with lucounu. He does have a lot of things that remind me of my dd13 at that age and she is HG, but I also know kids whose early childhoods didn't stand out as remarkable who turned out to be gifted and others who developed early who are not gifted at all.
Gifted wasn't on my personal radar until my oldest was about six so I guess that I wasn't paying attention to much other than her serious sensory issues, intensity, and my lack of sleep due to her constant screaming at that age - lol! I wouldn't worry terribly about where he falls in terms of IQ at this point but keep it in the back of your mind for later as you are getting closer to him starting school or homeschooling if that is where your family goes.
As far as feeling like you cannot share his milestones with other parents, do you have anyone with whom you can just share the joy of your child without worrying about it appearing competitive? Grandparents? Childless friends or ones whose kids are much older?
There is something about parenting that does bring out the worst in people in terms of it feeling like a competition. I remember it becoming worse, honestly, when dd13 was in elementary school b/c so many other parents were so focused on reading levels and one in particular quizzed my kiddo incessantly about what level she was reading at, 'can you read this to me, my kid is reading at this level,' etc. Now that she's in high school the parental pissing contest seems to have mellowed a bit, thankfully.
I'd expect that the feeling of needing to hide isn't going to get a lot better for some time if your child is standing out as being different than most of his peers in many ways. I struggled with not making dd feel like she should pretend to be someone she wasn't to appear typical and with not using her weaknesses as a way to assuage others' insecurities. For instance, she was a late walker and generally slower on gross motor skills (riding a bike, etc.). It is easy to fall into downplaying strengths by pointing out all of the ways in which the child is average or below as well.
