I know exactly how the OP feels, I stopped reading those "milestone emails" that I used to get. DD was never on track with those things...She walked at 11 months, but she has just now started learning words at 15 months. I feel like she was using all her energy on learning to walk and now that she has that down, she is focusing on words. Especially since she is learning so many words so quickly. Just in the past week or two she has gone from using one or two words to using six or seven. And she is also signing, even though I haven't really taught her much...As far as the "so big" game goes, I think it is great because DD learned the sign for "big" in this way. Plus it shows that she is understanding what I am saying to her.(Not to mention how much she loves it, and she gets a huge smile on her face when she does it, which is so cute, but I digress.)
A couple of weeks ago I went to an LLL potluck and one of the children there was almost exactly DD's age and she had so many words! (Including Mama, which DD has yet to say.)I felt very inadequate ( and a bit jealous) as a parent because at that time, the extent of DD's spoken vocabulary was "Hi"...The other little girl was saying hot, mama, please (!) and quite a few other words I can't remember at this time. As of today, DD says dada, kitty cat, doggie, hi, uh oh, cookie, and I think she is working on thank you...These words were in there all the time, but now she can actually get them out. It's like when I was trying to teach her to clap her hands and play peek a boo. One day she just did it out of the blue with no prompting from me. Now she claps her hands whenever she hears applause on the tv or the radio.
Whenever I start talking to my MIL about my worries re developmental progress, she always says "in five years you won't even remember when she started saying cat" Well, I probably will, but I get her point, which is that in the long run it doesn't really matter if she says it at ten months or twenty, the fact is she will eventually say it, and stop worrying already, lol.
I agree with other posters that some parents exaggerate or outright make up stuff about their kids..When DD started walking I had people coming up to me telling me that their daughter/son/grandson/nephew etc walked at 7/8/9/10 months... I am not saying that a child couldn't walk early, but 7 months?? I have yet to see that, and that is the only way I will believe it.
As far as drinking from a cup goes, DD does drink well from a cup because I started her off very early, like seven months-using a shot glass. But she cannot hold it on her own because she will dump it, and she still takes a sip sometimes and lets it all dribble out of her mouth. So don't feel bad. I started out anti-sippy, but now DD has one and uses it for meals mostly, but I also give her water between meals. She also loves to suck on her spray bottle.
I wouldn't shun your friends unless they are purposely trying to one up you, and it doesn't sound to me like they are-just being doting parents, IMO. DD gets so much out of playing with other kids her age and older, it really speeds up her development a lot. I know it can be hard seeing other people's kids doing more than yours, but if your DC is around them, he will pick up stuff a lot faster. Also keep in mind that as a parent, you may not see your child developing quickly because you see him every day..Other people may notice things you do not and point them out to you. In fact, I stated reading Baby Signs yesterday, and it made me realize how much DD actually has been communicating non-verbally, I just didn't realize it consciously.
You sound like a great parent who is very involved and very caring, and your son is normal, so just enjoy him and this time, because it will go soo fast!! I saw this bumper sticker once and it still cracks me up-"we spend the first two years teaching them to stand up and talk, and the next 16 telling them to sit down and shut up"