There's still some more tuning you can do for the shuttle with regards to taking off unnecessary engines, parts and fuel, but it's a big improvement from the beginning so I think you deserve the badge now.
Remember this isn't the end, but the start of the beginning.
If you try a new design from scratch, I'm sure that will showcase your skill improvements.
As for the reusability one...
For starters you should optimise your first stage more for easy landing. So landing legs, etc.
And remember that the optimal point of staging for reusable two stage rockets is a bit earlier than you'd otherwise expect.... So that you don't need TOO MUCH fuel to reverse the trajectory of the first stage back to the launchpad.
As for the second stage, working on the ground to reload it is a pain, simple as possible is good.
Do you even need traditional fairings or can you make a cargo bay from interstages