My 18 year old daughter didn't walk till she was almost 13 months old. She wasn't interested at all in walking! She talked very early, mind you, but she could get to where she wanted to go by crawling. I remember worrying about it, but the doctors told me that she would walk when she was ready....and she did.
Your little one will walk when he's ready. Don't feel pressured by what people say and don't let yourself get upset by those who judge. You have a beautiful, glorious child who will walk when he's ready.
As far as size goes...if your paediatrician isn't concerned, then that's the main thing. He sure is a cutie. Don't let what others say get you down. They have their own problems and by insulting you and your child it makes them feel better about themselves.
You're blessed with a beautiful boy