1. There's no guarantee that he acted alone and or without outside sponsorship.
2. There's no guarantee that all the information that he took was released publicly. It would be helpful to know the extent of what was taken, and who else knows it.
3. It would be helpful to know what other intelligence services have asked him/taken from him.
4 "To encourage the others"
That has been debated and put to rest.
Our elected officials initially tried to say he was a Russian spy, but could not provide any evidence to support the claim.
If he were a foreign asset, like for the Russians, for example, he would not have acted the way he did. In fact, his handlers would have preferred that he continued to operate in secret and continue to feed them as much info as he can.
The NSA could guess what he had access to, but it's harder to know what he still has. That's a very scary known unknown.