Hello,
From your symptoms, it appears totally normal.
In guys, usually epiphysis closure occurs by 20 or 21 yrs, or even earlier in some. It varies from one person to the other. So therefore, growth can occur till the epiphysis closure. If you have cosmetic worries about it, you still might have chances to get it corrected. You can take an X-ray and see if your epiphysis closure has occurred.
But, before that you need to have counseling, not that you are psychologically affected or something it's just to boost your self esteem. Your problem with breathing through mouth has to be checked if you have DNS.
You can see a orthopaedician and see if you can do anything about correcting your jaw line.
Thank you.