i have a friend who has a son who sleeps like your son seems to, and he's an amazing little kid. I wouldn't worry. He just sounds like he likes to snooze! He'll drop one one day and you probably will wish he hadn't haha!

As for the fontanelle. They usdually close between 6 and 18 months. Give or take. I was at the other end of the spectrum to you and DS's closed when he was about 4 months so we had to do the whole Paed thing. He is just at the other end of average, and his head is still growing perfectly, so I wouldn't worry too much about that either