Welcome, I'm pretty new here myself.
Your DS sounds like he's doing fantastic! I completely understand the exhaustion that comes from feeding a learning-hungry kid. I'm just grateful we have the internet. I think we would have had to live at the library back in the day.
We knew our DS was ahead at 3 (with reading, math, science), but we really didn't think it was that unusual (as first time parents also). Our goal with preschool at 3 was to give him a place to socialize and have fun (he only went 2 days a week). He has a late-late summer birthday, so he was always with kids up to a year older than him and did well with this.
I never found another kid in his school that was doing the things he was - but he did get a lot of benefit socially and creatively. He learned to be more independent at school and how to sit still to listen to a book (he REALLY struggled with this), how to walk quietly in line, raise his hand, etc. Those things may sound trivial, but I could see that these successes fed my DS' self-esteem.
We just continued at home to provide him hands-on learning experiences and play time. We figured he would have years and years of academic opportunities ahead of him.
I have been encouraged (on here) to wait until my DS is 6 for more accurate testing.
