You're right in that you can't change your username. Did you use the number as your username? There is an option that you can click on to automatically use the number instead of your username. I was thinking you had that checked.
You'll have to play with the pictures as an avatar. If you're posting a picture of your stones, they always seem to be overly large and blurry.
Sounds like you are getting some good results. Make sure you drink a lot of water. The ES will dehydrate you.