firstly - calm down dude
As said, the average length is only like 5.5inches or something?Also, you know that when you're looking down on your own penis it looks smaller than it will look to someone looking directly at it so that's probably a factor. Ignore 90% of the what your male friends are telling you about theirs because they're probably exaggerating:')
Like you've said, your dad didn't properly hit puberty until age 17 and you're not even 16 yet. Sometimes puberty does come later but you're probably worrying over nothing