Although we only had my youngest daughter's hearing tested, we had similar worries about her development initially. She rarely spoke until she was five (only grunts most often). Shocking to us because our first was speaking complete sentences before she turned two (honest, I have Xmas videos where she is making short sentences about Santa Claus and the Christmas tree when she was 15 months).
The youngest just won 2 academic prizes in her fourth grade class and has a vocabulary if not superior to, certainly as large as her older sibling's.
When she was younger (3-5 years old) several of her day care providers told us they thought she was autistic. Happily, turned out to be completely unwarranted.
I hope and believe your son will do fine. Personally, I have to guard against wanting my wee ones to grow up too fast. Don't know about the more civilized folk north of the border, but far too many down here haven't the patience to let children be children.
Glad to hear things are looking up.