welcome...it's not "average" and you likely are in the right place
I would say the parents here actually are experts. We are experts on our own children and children "like" ours (I use quotes because you won't BELIEVE some of the specific examples of sameness while comparing your child to those around him and seeing how unlike the average child he probably is). And there are also plenty of parents here who are also psychologists, educators, etc...
Your son in not average. A vocabulary of 100+ words at 19mo is not average. My 2nd DD was using appropriate complete sentances around that age...I'll never forget "Look, in the blue sky, an airplane." coming from the back seat. I almost wrecked the car!
I would bring home a book or two on "average" milestones and behavior, like what to expect from you 2 yo and leave those around for DH to read as well...and start planning now for early kindergarden or a first grade skip...or homeschool.
I agree with "enjoy the journey" advice. Just enjoy your son's uniqueness and get ready
