I didn't read the early pages of this thread. But based on your update, it definitely sounds like you have a gifted child on your hands! He sounds like a sweetie!
If I may-- I just want to throw out one caution for you: please avoid making his development a competition. It doesn't matter whether your son is a bigger talker now or not, or whether he will catch up to age-peers in a big way. He's on his own development curve. Your job is to provide him with the love, stimulation and encouragement to help him be happy and fulfilled. He'll probably enjoy museums, chapter books, documentaries and many other things earlier than most children. But please don't bother with what other kids are doing and just feed him what he needs.
Also, in regards to your son's interests-- whether it's trains or smells-- those aren't an indication of his giftedness, but instead of his interests. I don't see why you need to feel embarrassed to add that to your mom discussions! It's fun and quirky! My friends and I would have gotten a good chuckle out of a child who loved smells, and pondered where it would lead. (Also, FYI, my son is well above the DYS cutoff (and is a DYS) and he loved trains and cars as a toddler, so it's not an indication of intelligence to "not" like them.)
So glad you're having so much fun with your little guy. Those are very special years!
